bluuebunny/crossref_metadata_2025 huggingface dataset:
Clay Mineral Distribution in the Soil Areas of Arkansas
Authors: Garey C. L.
Published: August 2006

Studies on clay types in the soils of Arkansas show differences that are important to the soil properties in the soils of the various regions. Part of the agricultural importance of these soils may be related to their mineralogical composition.

The Mississippi River delta area has deposits of soil materials high in montmorillonite-type clay and possessing strong expansion and shrinkage properties. The Arkansas River valley has materials high in illite clay types with montmorillonite. Soils of the Coastal Plain predominate in kaolinite mineral but have sufficient quantities of vermiculite clay to dominate the chemical properties. The Ozark upland soils contain kaolinite and illite in varying proportions.

Much of the state is covered with a silt mantle of varying thickness in which the clay mineral composition is mainly that of montmorillonite and illite.
Muscovite Weathering in a Soil Developed in the Virginia Piedmont
Authors: Rich C. I.
Published: August 2006

A study was made of the weathering of musco vite-type mica to dioctahedral vermiculite in soils formed from Wissahickon schist in the Piedmont of Virginia. The trend of weathering as a function of depth was most apparent in the soil fractions from 20 to 0.2 microns. X-ray diffraction and chemical analyses indicate loss of potassium and expansion of the muscovite to form vermiculite as weathering proceeded. The amount of interstratified illite-vermiculite relative to vermiculite varied greatly between three soils and was characteristic for each. The widespread occurrence of dioctahedral vermiculite in highly weathered and acid soils suggests the formation of this mineral from commonly occurring muscovite-type micas.
Clay Mineralogy of Pennsylvanian Sediments in Southern Illinois
Authors: Glass Herbert D.
Published: August 2006

Controversy over the origin of clay minerals in ancient sediments arises because it is difficult to segregate the factors that cause differences in clay mineral composition. A plan of sampling based on four contrasts was used to evaluate some of these factors. Contrasts studied were: (1) permeability contrasts (sandstone vs. shales); (2) environmental contrasts (cyclic sedimentation); (3) weathering contrasts (outcrop vs. core); (4) source area contrasts (orthoquartzite facies vs. subgraywacke facies).

The resultant data indicate that clay minerals are both allogenic and authigenic. Allogenic clay minerals are the rule when inheritance from the source area dominates either postdepositional or environmental effect; authigenic clay minerals are found where the environment dominates. Rapid sedimentation favors a dominance of allogenic clay minerals, and major depositional environmental effects are required to produce appreciable change. Some of the factors that influence clay mineral composition include source area contribution, the depositional environment, postdepositional effects after burial, permeability, and postdepositional weathering effects.
Clay Minerals at a Pennsylvanian Disconformity
Authors: Dalton Jane A. , Swineford Ada , Jewett J. M.
Published: August 2006

At the Desmoinesian-Missourian disconformity in southeastern Kansas a fossil soil zone is recognized by variations in clay mineralogy in the uppermost Desmoinesian Holdenville shale, which underlies basal Missourian Hepler sandstone. The clay fraction of the overlying basal Missourian Hepler sandstone contains kaolinite, slightly hydrated illite, quartz, and vermiculite. Chlorite (rather than vermiculite) is present in shaly portions of the basal Hepler sandstone. Clay-size minerals of the typical Holdenville shale (marine) are predominantly illite, chlorite, quartz, feldspar, and a very small quantity of kaolinite. The clay-mineral assemblages in samples from the upper part of the Holdenville shale indicate hydration of illite, sporadic increase in kaolinite, possible decrease in feldspar, and progressive modification and destruction of chlorite resulting in production of mixed-layer minerals.
Current Progress in Silicate Structures
Authors: Bradley W. F.
Published: August 2006

Attention is called to the value to be derived from application of diffraction analysis of modern grade to specific, familiar, approximately known crystallizations. Features consequent to ordering of coordination polyhedra of differing sizes in layer structures are discussed, and their bearing upon relations between lattice parameters and chemical compositions are outlined.
The Dehydration of Tobermorite
Authors: Taylor H. F. W.
Published: August 2006

Tobermorite [Ca4 (Si6O18H2)Ca·4H2O] is a hydrated calcium silicate mineral with a layer structure which in some respects resembles that of vermiculite. Its dehydration has been studied using single crystals from Ballycraigy, N. Ireland. The three most frequently encountered hydration states are characterized by basal spacings (d002) of 14.0, 11.3 and 9.35Å. Dehydration to the 9.35Å state is complete by 300°C and is accompanied by a stacking change so that the pseudo-cell (a 5.58, b 3.66, c 18.70Å) becomes A-face centered. The 9.35Å structure persists up to 700°C, by which temperature all the water has been expelled, and there is some evidence that interlayer Si-O-Si bonds are formed to an increasing extent as the temperature rises.

At about 800°C, the 9.35Å hydrate changes to β-CaSiO3 twinned in two orientations. The b-axis of the 9.35Å hydrate becomes b for both orientations of the product, and the (201) planes of the latter are formed parallel to the (101̄) and (101) planes of the original material. The mechanism of the change is discussed and is compared with some other transformations occurring under similar conditions. An orientation-determining step is suggested in which the principal effect is a migration of silicon atoms or ions, the calcium—oxygen skeleton remaining relatively undisturbed.
Studies on the Size and Shape of Clay Particles in Aqueous Suspension
Authors: Kahn Allan
Published: August 2006

The size and shape of clay particles in aqueous suspension have been determined by means of five experimental techniques—electro-optical birefringence, ultracentrifugation, viscometry, optical transmission and electron microscopy. Five clay minerals—montmorillonite, illite, hectorite, nontronite and attapulgite—each subdivided into five size fractions, were studied. The average particle dimensions in each fraction are tabulated.

An evaluation of the experimental techniques is presented. It is concluded that for a preliminary survey of the particle size and shape of clay minerals the technique of electron microscopy is best. However, once a model for the particles is obtained, a combination of the techniques of electro-optical birefringence and viscometry becomes more useful in characterizing the size and shape of the particles in suspension.
Water-Vapor Adsorption on Clays
Authors: Johansen Robert T. , Dunning H. N.
Published: August 2006

The distinctive response of clay minerals to water indicated that it should be possible to determine the water sensitivities of sedimentary rock samples directly by water- vapor adsorption measurements. Therefore, the adsorption of water-vapor by standard clay samples and by core samples from oil-producing formations has been investigated.

Water-vapor adsorption isotherms of the montmorillonite and kaolinite samples are characteristic of the clay type and serve as an aid in their identification. The illite isotherm was intermediate between those of the other two types.

Water-vapor adsorption by core samples from oil-producing formations varied with the contents of swelling clays and with water-sensitivities as indicated by previous x-ray analyses and permeability studies. Core samples containing montmorillonite clay adsorbed water vapor strongly and exhibited typical adsorption—desorption hysteresis. Correlations of nitrogen and water-vapor adsorption studies with clay analyses and permeability measurements show that the water-vapor adsorption method is a promising means for the direct measurement of the water sensitivities of sedimentary formations.
Water-Vapor Sorption on Kaolinite: Hysteresis
Authors: Martin R. Torrence
Published: August 2006

Detailed water-vapor sorption measurements were made on Li, ISTa, K, Cs and Mg kaolinite at 25°C. When desorption is started from P/P0 near saturation, all ionic modifications show reversible hysteresis. The size and P/P0 range of the hysteresis loop varies with the nature of the exchangeable ion and sample history.

No hysteresis occurs on Li and K kaolinite when desorption is started at P/P0 < 0.8 which along with other data indicates that Li and K exchangeable ions are not truly hydrated below P/P0 = 0.8. The hysteresis for all ionic modifications is traced to hydration of the exchangeable ions. The apparent anomalous position of Li and K ionic hydration is attributed to control of hydration of exchangeable ions by the difference between the hydration energy of the ion minus the specific adsorption energy of the ion for the clay. This difference must be positive before true ionic hydration occurs.

A molecular model for sorption is postulated in which sorption is assumed to take place at specific sorption sites upon the clay surface. The energy of sorption at different sites is believed to be different and also to be a function of the hydration state of the exchangeable ion. By the use of the proposed model and the detailed sorption data, hydration of the different exchangeable ions as a function of the relative vapor pressure can be obtained. The sorption model also predicts phase changes in the sorbed film at certain relative pressures. These calculated phase changes agree very well with phase changes indicated from Jura-Harkins’ plots of the experimental data.
Stability and Decomposition Products of Hectorite
Authors: Sand L. B. , Ames L. L.
Published: August 2006

The Hector, California, bentonite has been found unusual in many respects, and its thermal stability under hydrothermal conditions is no exception. It is important that the stability of this bentonite be known, as it is an end member of the saponite series with all cation positions, excluding interlayer, in the structure filled. The information is applicable to studies of wall rock alteration in which saponites occur as alteration products associated with ore deposition.

This saponite has an upper thermal stability limit of 750°C, at 15,000 psi water pressure, at which temperature it decomposes. The only products observed were talc and vapor; above 780°C the decomposition products observed were anthophyllite and vapor. Syntheses on the hectorite composition corroborate these decomposition temperatures and products.

Hydrothermal treatment at temperatures below about 450°C produce no change in the x-ray diffraction pattern of hectorite: on drying, the lattice collapses to a basal spacing (10–12Å) approaching that of mica, and with ethylene glycol expands to 17Å. However, after hydrothermal treatment above this temperature and to decomposition at 750°C, the hectorite, after subsequent cooling, collapses on drying at 110°C or less to 9.4Å, but expands as before to 17 Å with glycol saturation. Without the glycol treatment the resulting material could be mistaken for talc and considered the decomposition product of hectorite at the higher temperatures. This behavior also occurs using the synthetic hectorite but does not occur when using synthetic or natural saponites containing aluminum.

For comparison, the relative stabilities of some dioctahedral and trioctahedral layered minerals are given to show the consistently higher stabilities for the minerals whose octahedral positions are filled.
Surface Area Changes of a Vermiculite by Acid and Thermal Treatment
Authors: Lopez-Gonzalez Juan de D. , Cano-Ruiz Jesus
Published: August 2006

A Vermiculite from Beni-Uxera, North Africa, was refluxed with HC1 solutions of various concentrations to determine the effect of such a treatment on its surface area. The treated vermiculite was analyzed for “free” SiO2 and by x-ray diffraction, and the refluxing solutions were analyzed for the cations removed from the vermiculite. Surface areas were determined by means of adsorption isotherms of n-butane at 0°C.

The surface area of the acid-treated vermiculite increases with increase in concentration of the acid. Heating of the acid-treated samples or the natural samples decreases the surface area.

The increase in surface area by acid treatment is due to destruction of the vermiculite and its conversion to a “free” form of SiO2 which possesses a large surface area. x-Ray analysis indicated that this “free” SiO2 was not present in the interlayer positions of the crystal lattice of vermiculite.
Pretreatment of Soils and Clays for Measurement of External Surface Area by Glycerol Retention
Authors: Kinter Earl B. , Diamond Sidney
Published: August 2006

Heat treatment at 600°C has been the usual procedure for irreversible collapse of expanding clay minerals prior to determination of the external surface area of clays and soils by glycerol retention. Evidence is presented showing that this treatment is unsuitable since it greatly reduces the external surface area of certain minerals and increases that of others. Saturation with the triethylammonium cation avoids these difficulties and produces an effect analogous to the collapse of expanding minerals by stabilizing their basal spacing at 13.3 Å. This prevents the entrance of glycerol between the unit layers and confines the sorption to the external surfaces of the particles.
Quantitative X-Ray Determinations of Some Aluminous Clay Minerals in Rocks
Authors: Schultz Leonard G.
Published: August 2006

x-ray diffraction traces were made of oriented aggregates of artificial binary mixtures containing approximately equal, weighed amounts of samples of illite, montmorillonite, mixed-layered combinations of illite and montmorillonite, and of kaolinite samples having different degrees of crystallinity. Measurements most suitable for quantitative purposes were obtained from the 7 Å kaolinite peaks and from the 10 Å peaks of illite and collapsed montmorillonite and collapsed mixed-layer clay. In this paper the sum of five height measurements at half-degree intervals across the peak are considered to be a measure of the area of the peak. Fireclay-type kaolinites gave 7 Å peak areas about equal to the area of the 10 Å peak of an equal amount of illite, montmorillonite, or mixed-layer clay, whereas well-crystallized kaolinites gave 7 Å peak areas generally about twice that of the 10 Å peak of an equal weight of the illite-montmorillonite minerals. Kaolinite samples having intermediate degrees of crystallinity gave 7 Å/10 Å peak area ratios intermediate between 1: 1 and 2:1. The shape of the 7 Å kaolinite peak was used to evaluate the crystallinity of the kaolinite.

x-ray diffraction characteristics of the chlorite minerals from the different groups of sedimentary rocks studied vary considerably, and no uniform method has been found for their evaluation.
Advances in X-Ray Diffractometry of Clay Minerals
Authors: Parrish William
Published: August 2006

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

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

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

Glycerol-ethanol sodium salted clay pastes prepared from clays extracted directly from the soils and not allowed to dry were found to yield superior x-ray diffraction diagrams for the identification of the major clay minerals than pastes prepared from clays that suffered dehydration after extraction.

Prevention of drying of soil clays after their extraction from the soils is essential for proper identification of the clay minerals. This is particularly true for identification of hydrated halloysite and for differentiation between high exchange forms and low exchange forms of montmorillonite. This differentiation is based on the finding that glycerol-ethanol salted potassium-saturated montmorillonite pastes prepared from clay suspensions have a 001 spacing of 18.5 Å whenever the exchange capacity ranges between 92 and 95 meq/100 g oven-dry clay, and 14.5 Å whenever the exchange capacity ranges between 115 and 135 meq/100 g. Either both these spacings or a mixed-layer spacing appears in montmorillonites having exchange capacities between 95 and 115 meq/100 g.

Saturation of pure vermiculite minerals brings about contraction in the 001 spacing from 14.2 Å to 10.6 Å only after air drying in those forms with exchange capacities ranging between 200 and 207 meq/100 g water-free mineral, but in vermiculites with an exchange capacity of 250 meq/100 g this contraction occurs even without drying. Both of these forms of vermiculite are found in soils.

Several sets of “standardized” natural clay mineral mixtures are necessary for quantitative x-ray analysis of soil clays.
Further Correlations of Kaolinite Crystallinity with Chemical and Physical Properties
Authors: Murray Haydn H. , Lyons Sanford C.
Published: August 2006

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

Fireclay deposits occur in Latah County, Idaho, as residual weathered products, and as lacustrine sediments comprising part of the Miocene Latah formation. The residual deposits were developed upon granitic (granodioritic, gneissic) masses by surface weathering. The lacustrine fireclays were derived dominantly from weathered residuum and to a minor extent from volcanic ash.

Mineral proportions in the residual clay are typically as follows: kaolin minerals, 65 percent; quartz, 20 percent; K-bearing micas, 12 percent; and montmorillonite-chlorite mixed-layer clay, trace.

The sedimentary fireclay deposits range widely in clay content, from some that are almost wholly kaolin to others containing as little clay as the residual material, or alternatively, to those meeting minimal requirements of fireclay. As the content of kaolin decreases in the deposits, there is a corresponding increase in content of quartz, K-bearing micas, and in the less abundant components orthoclase, mixed-layer illite— montmorillonite, and mixed-layer chlorite—montmorillonite.

In both the transported and residual clay bodies the kaolin minerals are, in order of decreasing abundance, halloysite, endellite, and fireclay mineral.

The lake deposits also contain seams of poorly crystallized kaolin that is inferred to have been derived from volcanic ash because (1) it contains minor quantities of tridymite, sanidine, and volcanic glass, and (2) it contains notably more endellite and allophane (amorphous and relatively soluble in NaOH) than is present in the other kaolin deposits. Endellite seemingly has developed in two separate geologic environments: as an alteration product of granodiorite gneiss by surface weathering and as an alteration product of volcanic ash deposited and altered in a fresh-water lake. It is postulated that endellite is a relatively common product of weathering.
Ion Adsorption on Clays: A Review
Authors: van Olphen H.
Published: August 2006

The following ion-adsorption processes may occur on a solid surface, in contact with an ionic solution. An electric double layer is created by:

1.

Specific adsorption of certain ions (the “potential determining ions”) which give the surface a positive or a negative charge, unless, as in the case of the layer surface of a clay, the charge originates from interior crystal lattice imperfections.

2.

Accumulation of “counter ions” (“gegenions”) close to the charged surface in the liquid.

In an established double layer there may occur:

1.

Exchange of counter ions for other species of the same sign available in solution (exchange adsorption).

2.

Chemisorption of ions on the surface, which may lead to destruction of the double layer or to the creation of a new double layer, possibly of opposite sign.

3.

Exchange of exposed lattice ions at the surface by ions in solution (lattice exchange).

Therefore, in a single double layer several possibilities must be considered when interpreting adsorption data. In the case of clays, an additional complication arises in that two different double layers are involved simultaneously—the layer surface double layer and the edge double layer.

The layer surface double layer originates from interior lattice substitutions; the edge double layer originates from the adsorption of potential determining ions on the broken-bond surface. The layer surface double layer is negatively charged; the edge surface double layer probably is amphoteric and may be either positive or negative depending on the composition of the solution.

Technically, the two most important adsorption phenomena in clays are the cation exchange adsorption on the layer surfaces and chemisorption of anions at the edge surfaces. Our present knowledge on these two topics will be reviewed from the point of view of the electric double layer theory.
Cation Exchange Behavior of Vermiculite-Biotite Mixtures
Authors: Frysinger Galen R.
Published: August 2006

The cation exchange capacity of a series of commercially available vermiculite-biotite minerals (Traveler’s Best, South Carolina; Libby, Montana; and Polobora, South Africa) was measured by a column method using various cations. The selectivity of the clay mineral for various ion pairs was determined with particular attention given to the adsorption from a sodium chloride-cesium chloride mixed electrolyte solution. The mineral was found to be highly selective for cesium ion, a large part of the amount adsorbed probably replacing potassium ions in the biotite layers. This replacement in the biotite is a much slower process than normal ion exchange and greatly lengthened the time required to come to equilibrium in the column.

The cesium ion cannot be removed easily from cesium-saturated vermiculite. The fixation of cesium ion was close to 100 percent at room temperature in contact with a cesium chloride solution. An isotopic exchange, Cs 133 for Cs 134, removed only very small quantities of the fixed cesium. Boiling with sodium chloride was only slightly more effective. All the results are in general agreement with the theory explaining ion fixation on the basis of collapse of the vermiculite structure to that of biotite.
Behavior of Moist Soils in a Thermal Energy Field
Authors: Winterkorn Hans F.
Published: August 2006

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

Pore fluid pressures that develop within soil masses as a result of both mechanical and physico-chemical effects influence the magnitude of the intergranular or effective stresses. The intergranular stresses control, in many cases, soil behavior in shear and compression. The physical significance of pore water pressure in a cohesive soil is examined in terms of several components which combine to give the total pressure. An analysis of fluid pressures at various points within a soil mass based on a condition of no flow at equilibrium shows that changes in any one component of the total pressure from point to point are offset by changes in other components.

The analysis shows that a pore pressure measurement reflects interparticle repulsive pressures and water adsorptive forces as well as purely hydrostatic pressures arising from mechanical effects. The individual components of total pore pressure are not directly measurable except in special systems. Data are presented which indicate that a significant portion of the swell of a compacted soil is attributable to water pressure deficiencies caused by mechanical and capillary components which act in addition to osmotic pressure components.

Component water pressures are related to stresses between particles. It is shown that intergranular pressures are dependent on osmotic and adsorptive components of the total water pressure.
Shear Strength of Montmorillonite and Kaolinite Related to Interparticle Forces
Authors: Warkentin B. P. , Yong R. N.
Published: August 2006

Shear strength of saturated, remolded clay mineral samples was measured in an attempt to relate strength to forces acting between clay particles. The fine fractions of the clays, purified when necessary, were consolidated to different void ratios and subjected to quick, translatory shear in a direct shear device. Relative values for shear strength were obtained in this way. Interparticle forces in the clays were altered and the effect on shear strength was observed.

For a high-swelling, Na-saturated montmorillonite, strength at constant void ratio decreased with increasing salt concentration. To explain the decrease in strength with decrease in force of repulsion between particles a model is suggested where strength results from the force of repulsion resisting displacement of particles in the shear plane. Addition of small amounts of dispersing and of soil-conditioning chemicals had little effect on shear strength.

Calcium montmorillonite had a lower strength than sodium montmorillonite when compared at the same void ratios. This is related to the lower surface area of interaction and lower repulsion found with divalent ions.

Water content at the liquid limit showed the same dependence upon interparticle forces in the montmorillonite clays as did shear strength.

In kaolinite, interparticle forces of attraction result in a structure or particle arrangement which has the major influence on shear strength. A clay at low pH which was flocculated in a network, edge-to-face structure owing to presence of positive edge-charge had higher strength than a dispersed clay, but a clay flocculated by electrolyte which produced a lamellar, face-to-face structure had a lower strength.
Flocculation of Selected Clays by Various Electrolytes
Authors: Hsi Huey-rong , Clifton Donald F.
Published: August 2006

The flocculation behavior of clay specimens from altered basalt, altered granodiorite, and a transported (?) deposit in Latah County, Idaho, was investigated in order to determine if flocculation behavior would be an aid in characterizing clay samples in a way that could be related to the origin and history of the clays. The clay minerals are of the kaolinite group.

As flocculants, various chlorides differ one hundred-fold and sodium salts twenty-fold in the concentrations necessary to flocculate a clay to a fixed settling rate. The concentrations of individual chlorides necessary to flocculate different clays vary three-fold and the concentrations of individual sodium salts vary ten-fold. In all cases the higher the valence of the cation the lower is the concentration required for flocculation; the relative effectiveness, however, varies with the clay. The relative effectiveness of the anions as flocculants varies greatly with the clay and no definite order of effectiveness is apparent.

Halloysite requires less electrolyte for flocculation and has a larger settling volume than kaolinite. Well crystallized kaolinite has a smaller settling volume than poorly crystallized kaolinite.

Wide differences of flocculation behavior may provide a valuable, rapid method of classifying the clays of a district.
Significance of Kaolinite Intersalation in Clay Mineral Analysis
Authors: Jackson M. L.
Published: August 2006

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

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

Some montmorillonites may be differentiated by complexing them with polyalcohols having a CH2 group that is not connected to an oxygen atom. Montmorillonites with a low layer charge and high valence interlayer cations have larger basal spacings for their complexes than do those with a high layer charge and low valence interlayer cations. The basal spacings of these complexes are relatively larger if the clay has a large initial water content. The spacings for some complexes which are initially equilibrated at very low humidities are small, indicative of little penetration by polyalcohol molecules. Polyalcohol molecules may have difficulty replacing water molecules that are associated with the interlayer cations. The spacings of complexes with ethylene glycol and glycerol do not depend upon the initial interlayer water content. Water molecules may be an essential component of mont-morillonite-polyalcohol complexes.

The polyalcohol molecules probably are associated with the clay surface through weak C-H···O interactions although virtually no shortening of this bond distance occurs. The C-H···O interaction is enhanced by the presence of higher valence interlayer cations. OH groups increase the thermal stability of complexes probably by interacting with the exchangeable cations. Longer chain molecules are held more tightly between the silicate sheets. One layer of polyalcohol molecules between silicate sheets is more stable than two layers. One layer of organic molecules is more stable with higher valence interlayer cations. Small molecules such as those of ethylene glycol may pack down somewhat into the “hexagonal holes” in the silicate surface.
Adsorption of Proteins, Enzymes and Antibiotics by Montmorillonite
Authors: Pinck Louis A.
Published: August 2006

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

Aliphatic chain molecules may be adsorbed on montmorillonite surfaces with the zigzag of their carbon chain either parallel or perpendicular to the surface. These orientations are designated αII and αI, respectively. Fourier syntheses have too few terms to distinguish clearly between these orientations. The problem is studied therefore by consideration of the basal spacings. These spacings are appreciably less than the sum of the van der Waals cross-section of the molecules plus the thickness of the montmorillonite layer. Chemical bonding or geometrical packing, or both, appear as possible explanations.

Previous studies have shown that CH activity influences the shape of the adsorption isotherms, but infrared studies of the adsorbed molecules have shown no appreciable change in the CH-stretching frequencies. This suggests the importance of the CH activity for organic—organic interaction on the clay surface rather than for clay-organic interaction itself.

The possibility of geometrical packing is studied by means of molecular models and it is shown that an appreciable contraction can occur at a clay-organic interlace owing to a keying of the molecules into the surface structure. This is possible equally well for the αII and the αI orientations.

From the information available, it appears that the αII arrangement is adopted by aliphatic chain molecules containing strongly polar groups in order to place the dipole parallel to the silicate surface, while the αI arrangement is favored by other aliphatic chain molecules possibly because this provides a favorable organic-organic interaction.
Mechanism of Stabilization of Cohesive Soils by Treatment with Organic Cations
Authors: Davidson D. T. , Demirel T. , Rosauer E. A.
Published: August 2006

The amount of moisture in a soil and its orientation to individual soil particles may be influenced by small additions of organic cationic compounds. Clay particles adsorb these cations, and because of their hydrophobic nature a waterproofing effect occurs. Thermodynamic considerations are presented to explain the strength retention of treated soils.
Formation of Dioctahedral Vermiculite in Virginia Soils
Authors: Rich C. I. , Cook M. G.
Published: August 2006

The weathering of micas to form the dioctahedral analogue of vermiculite is a common process in acid soils. Laboratory weathering of the micaceous 5–2μ fraction of parent materials of certain Virginia soils resulted in a product similar in character (whether mixtures of vermiculite and regularly and randomly interstratified mica—vermiculite, or vermiculite only) to those formed by natural weathering processes. The formation of vermiculite rather than (or, in addition to) kaolinite is attributed to substitution of Na and other ions for K, other structural imperfections, and the small size of the original mica flakes.

The low cation exchange capacity and stability, in contraction and expansion, of the 14Å product is attributed partly to retention of hydroxy-Al and Fe groups in the interlayer spaces. The removal of these interlayers by natural or laboratory processes results in a product that contracts easily but may or may not expand to 18 Å on glycerol solvation. This may be associated with the original charge of the mica as evidenced by its K and Na content.
A Glycol—Sodium Vermiculite Complex
Authors: Bradley W. F. , Weiss E. J. , Rowland R. A.
Published: August 2006

A complex of vermiculite with ethylene glycol was prepared by repeated boiling of a sodium-saturated cleavage flake in dry ethylene glycol. A stable product with a c period of 12.9 Å afforded 15 terms for a one-dimensional Fourier synthesis. A model composed of glycol molecules with the plane of the zigzag normal to the silicate face is found to be consistent with the observed diffraction data. The complex apparently conforms to a stoichiometric ratio of two molecules per unit cell per layer of vermiculite.
Organic Cation Exchange on Montmorillonite as Observed by Ultraviolet Analysis
Authors: McAtee James L.
Published: August 2006

An analytical method is described whereby the exchange of various organic cations for other organic cations on montmorillonite is determined. The exchange is followed by means of a Beckman DK-1 ultraviolet spectrometer.

It has been observed that organic cations from compounds such as primary, secondary, and tertiary amine salts and quaternary ammonium salts can be exchanged for one another on the natural cation exchange substance, montmorillonite. The exchange is carried out in isooctane to which a small amount of isopropyl alcohol has been added to aid in dispersion of the organic-clay complex. By choosing pairs of organic substances, of which one has strong absorbance in the ultraviolet and the other does not, the exchange can be followed quantitatively with the u.v. spectrometer.
An Improved Pretreatment for Mineralogical analysis of Samples Containing Organic Matter
Authors: Anderson J. U.
Published: August 2006

Organic matter removal is accomplished rapidly and efficiently without removing carbonates by treating samples with a sodium hypochlorite solution. Quantities of organic matter left in samples by this treatment are commonly less than remain after hydrogen peroxide treatment of acidified samples.

Stable suspensions result from the use of a sodium carbonate-sodium bicarbonate solution to wash and sodium saturate the samples without dissolving or complexing sesquioxides.
Cesium Sorption Reactions as Indicator of Clay Mineral Structures
Authors: Tamura Tsuneo
Published: August 2006

At low cesium ion concentrations extremely high selectivities for cesium are exhibited by layer lattice silicates with unexpanded 10 Å c-spacing. The total amount of cesium which can be sorbed by these minerals depends on the edge area and the exchange capacity. At a concentration of 10−5 meq of cesium and 5 meq of sodium, a sample of biotite representing less than 0.025 meq of exchange capacity sorbed over 90 per cent of the cesium and a hydrobiotite with 50 percent vermiculite and representing 1.0 meq of exchange capacity sorbed 80 percent of the cesium.

After heating bentonites to 500–700° C more cesium is sorbed from solutions containing high sodium concentrations by the heated bentonite than the original material. The change in the amount of cesium sorbed as a result of heating may be a useful property for detecting the presence of montmorillonite in mixed or interlayered mineral systems. Lattice expansion of biotite results in improved cesium sorption; this behavior is due to generation of sufficient favorable exchange sites to offset the loss of edges with favorable 10 Å spacing.
Clay Mineralogy of Mississippian Strata of Southeast Iowa
Authors: Hayes John B.
Published: August 2006

Clay mineral suites were extracted from 125 biocalcarenites, dolomites, mudstones and arenaceous rocks from the marine Keokuk, Warsaw and Salem formations of Mississippian age from southeast Iowa and nearby portions of Illinois and Missouri. Well crystallized illite, 2M1 polytype, randomly interstratified illite—montmorillonite, and quartz are in all clay suites. In the south part of the area, trioctahedral chlorite is absent or rare in Keokuk rocks, but is increasingly abundant upward in the section. Kaolinite is confined to the upper part of the section. In the north part of the area, the same upward order of appearance prevails, but the first appearances of chlorite and kaolinite are shifted downward in the stratigraphic section. This distribution of clay minerals is similar to that found by investigators in other areas: kaolinite confined near shore, chlorite in an intermediate position and illite concentrated farther from shore. Clay mineral evidence, combined with petrographic and stratigraphic data, strongly indicates that the type Mississippian strata of southeast Iowa were deposited in a southward regressing epicontinental sea.

Vermiculite and abundant mixed-layer illite-montmorillonite, weathering products of chlorite and illite, respectively, mark a local unconformity between lower and upper members of the Warsaw Formation on the crest of the Warsaw Anticline.
Experiments on the Decomposition of Silicates and Discussion of Chemical Weathering
Authors: Correns Carl W.
Published: August 2006

Experimental investigations of chemical weathering in which powders of potassium feldspar, albite, leucite, muscovite, tremolite, olivine, and volcanic glass are treated with pure water and with dilute solutions of sulfuric, carbonic, and hydrochloric acid have been performed in an apparatus in which the mineral powder is exposed to a circulating water flow. The experiments have been continued recently by treating kaolinite and montmorillonite. The course of decomposition of these minerals depends on water flow rate, grain size, temperature, and pH of the solutions. These experiments in open systems are compared with investigations reported in the literature and with the conditions of natural weathering.
Bentonite-Methylamlne Complexes
Authors: Rowland Richards A. , Weiss E. Joseph
Published: August 2006

Suspensions containing 3 percent sodium bentonite (Wyoming) and each of the four methylamine hydrochlorides were prepared so that the latter were present in amounts equal to 25, 50, 75, 100, 125, 200, 400, 600, 800, and 1000 percent of the exchange capacity of the clay. The flocculated clay was removed by decantation, and an oscillating -heating X-ray diffraction (Cu Kα.) pattern was made of the first-order diffraction maximum. With these patterns, the thermal stability, mixed layering, and multilayering of the amine-bentonite complex were followed. For methylamine, the data suggest that the first cations to enter lie in the holes with their C-N axes as close to the oxygen surface as possible. As additional methylamine hydrochloride enters, the C−N axis stands perpendicular in the holes to accommodate the chloride, and after all the holes are filled a second layer forms. Although the geometry of the dimethylamine cation permits it to occupy only two out of three holes, it also forms a second layer. The trimethylamine and tetramethyl ammonium cations are so large that they can occupy only one hole in three; this distribution satisfies the cation-exchange capacity, but a second layer does not form.