OH-A1 solutions were prepared by adding appropriate amounts of NaOH to A1C13 to obtain OH/Al mole ratios of 2.0, 2.5, 2.7, 3.0, and 3.3 in the final suspension. Solid Na2SO4 and Georgia kaolinite (KGa-2) were added individually and jointly to the OH-Al solutions. All samples were aged for 30, 70, and 180 d. X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectrometry were used to characterize precipitates. Bayerite, gibbsite, and nordstrandite crystallized at mole ratios of 3.0 and 3.3, with bayerite being the most abundant. A morphology of clusters of triangular pyramids is described for bayerite. Despite the aging duration, only noncrystalline Al compounds were obtained in mole ratios of 2.0, 2.5, or 2.7. The addition of sulfate to OH-A1 solutions in mole ratios of 2.0 and 2.5 produced crystalline basic aluminum sulfates of variable morphology, but with similar chemical compositions. These phases lost crystallinity with aging. The product from a 2.7 OH-Al solution was X-ray amorphous hydroxysulfate. In contrast, products obtained at mole ratios of 3.0 and 3.3 contained no sulfate ion, which restricted the formation of gibbsite, bayerite, and nordstrandite. The addition of kaolinite to the solutions in OH/A1 mole ratios of 3.0 and 3.3 favored the formation of nordstrandite. The simultaneous addition of sulfate and kaolinite to the OH-A1 solutions in mole ratios of 2.0 and 2.5 produced prevalent sulfate over kaolinite, whereas the opposite occurred at mole ratios 3.0 and 3.3.

Quaternary marine terrace deposits consisting of gravels interbedded with thin sandy gravel layers have been subjected to subaerial weathering. Restricted to the sandy gravel layers, allophane gel either replaced bytownite sands to form a pseudomorph or coated the pebbles. The allophane has an average Al/Si atomic ratio of 1.5 with 45% H2O. The sandy gravels were originally rich in bytownite (av. An86) sands derived from underlying Tertiary basaltic lapilli tuff. The highly soluble and aluminous bytownite favored the formation of allophane. In the sandy gravel layers, pebbles coated with allophane gel were almost fresh whereas those in the gravel layers were highly weathered to form halloysite-rich clays. Allophane gels acted as a somewhat impermeable geochemical barrier impeding a mineral-water reaction in the bytownite-rich sandy gravel layers and thus significantly retarding pebble weathering, while prolonged weathering in the gravel layers resulted in the severe decomposition of pebbles. Bytownite protected the pebbles against weathering, implying that minor soluble minerals might be one of the factors in the natural variation of the weathering rates of rocks and sediments.

Adsorption calorimetry was used to develop a method for determining the surface area of low-surface-area materials (<1 m2/g), which required no pretreatment of the surface, such as outgassing at elevated temperatures. The method involved flowing heptane through a small amount of sample (0.15 to 1.0 g) in the flow cell of a commercial microcalorimeter. When thermal equilibrium was reached at the powder-heptane interface, pure heptane was replaced with a heptane carrier-solution containing 0.6 volume % n-butanol (n-BuOH) as the preferential adsorbate. The integral enthalpy of preferential saturation adsorption, ΔHsat, of n-BuOH on the surface was found to be a function of the BET surface area of the sample. An empirical relationship between ΔHsat and BET surface area was determined over a surface area range of about three orders of magnitude (0.095 to 81 m2/g) by performing adsorption experiments on five α-alumina standard reference powders. The technique was applied to the determination of surface areas of untreated rock and mineral powders.

Kaolinite from the Black Ridge, Clermont, has relatively low δ18O (12.3‰ to 14.8‰) and very low δD values with a large variation (−120‰ to −85‰). Comparison of these data with those from the nearby Denison Trough and elsewhere in eastern Australia, together with previous studies of the mineralogy of the sedimentary rocks, suggests that extensive kaolinization of the “White Section” resulted from weathering during the Late Triassic to Early Jurassic periods. The relatively large variation in δD values of kaolinite probably derives from post-formational isotopic exchange with other fluids.

The similarity between δ18O values of kaolinites from Black Ridge and from the Denison Trough suggests that the small Miclere-Black Ridge basin may have been part of the Denison Trough before the Late-Triassic inversion. The preservation of original δD values in kaolinite at Black Ridge indicates that unlike the Denison Trough, which was reburied at more than 1000 m, the Miclere-Black Ridge basin was not rebuffed at great depth during the Mesozoic period.

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.”

Alumina-pillared montmorillonite is prepared by intercalation of polyoxyhydroxy aluminum cations (Al137+) of a natural montmorillonite from Dimitrovgrad, Bulgaria. Transmission electron microscopy, powder X-ray diffraction, energy dispersive X-ray spectroscopy, and surface area (BET) methods are used to study the untreated and pillared forms of the montmorillonite. A structural model involving deformed Al13 pillars is proposed. Four pillar types are derived and these pillars are uniformly distributed over the interlayer-cation positions of montmorillonite. Calculated electron diffraction patterns were simulated using the multi-slice method. The structural model explains the increased ordering along the c axis of the pillared form compared with the untreated montmorillonite. The model explains the structure of a pillared montmorillonite with different distributions of the pillars in the interlayer. The proposed model is consistent with the observed data.

Although the wide range of minerals resulting from alteration of tuffaceous rocks under hydrothermal and weathering conditions is well known, the extent of variation in composition of discrete bentonite beds subjected only to normal diagenesis and compaction is perhaps less well known.

Three bentonite samples from the Atoka Formation of Pennsylvanian age are predominantly mixed-layer illite-montmorillonite with subordinate kaolinite. Most bentonites in the Fierre Shale of Late Cretaceous age are entirely montmorillonite, but a few contain some kaolinite; one is predominantly kaolinite; some also contain appreciable interlayer Al(OH)3 or Mg(OH)2 forming a mixed-layer montmorillonite-chlorite clay; several are composed of considerable clinoptilolite, and one is largely phillipsite. Bentonite beds in the Carmel Formation of Middle and Late Jurassic age differ among themselves in composition; in a few, illite is the dominant clay; in others, mixed-layer chlorite-montmorillonite-illite in different proportions is the dominant clay; kaolinite is common and makes up nearly half of one sample. A rhyolite tuff near Denver, Colorado, has been altered to halloysite. Reasons for variation in the composition of these bentonites are only partly understood.

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.

Formulas calculated from analyses, written in the fractional notation used by Ross and Hendricks, and with a notation of tetrahedral and octahedral charge, reveal relationships between the hydrous micas called “illite,” montmorillonites (using the term in the restricted sense), and beidellites not otherwise apparent. These relationships are shown graphically by means of histograms made up of five columns, representing respectively, total charge, tetrahedral charge, octahedral charge, potassium, and water.

“Illites” have a much higher total charge and a much higher tetrahedral charge than montmorillonites, of which the tetrahedral charge is usually insignificant. Consequently simple removal of fixed K and its replacement by exchangeable cations would not convert an “illite” to a montmorillonite nor would mere fixation of K between the layers of a montmorillonite result in the formation of an “illite” like any that have been described.

From the standpoint of octahedral-tetrahedral charge relationships, beidellites and “illites” should be more similar than montmorillonites and “illites.” However, considerable doubt has been cast by Grim and Rowland on the purity of most of the materials that have been called beidellites; they interpreted the differential thermal curves of the beidellites examined by them as indicating mixtures of kaolinite or halloy-site, “illite,” and montmorillonite. Formulas based on calculated mixtures of these minerals in varying proportions were very similar to formulas calculated from analyses of the so-called beidellites. Thus the existence of a montmorillonite clay like that which would be formed if the fixed K in “illite” were removed and replaced by exchangeable cations has not been authenticated and the concept that montmorillonite and “illite” are analogous except for the presence or absence of nonexchangeable potassium is misleading and is an oversimplification of the relationship between the two groups of minerals.

DNA manipulation is crucial for many biotechnological prospects and for medical applications such as gene therapy. This requires the amplification and extraction of DNA from bacteria and the transfer of these DNA molecules into cells, including bacterial and mammalian cells. The capacity of the natural magnesium silicate clay mineral sepiolite to bind to DNA makes it a potentially useful tool for biotechnological/medical strategies. In addition, sepiolite is inexpensive and classified as non-toxic and non-carcinogenic. This review will first describe the physicochemical interactions between sepiolite and DNA. Then, the leverage of sepiolite/DNA interactions for DNA extraction from bacteria, to optimize DNA transfer into bacteria and DNA transfection into mammalian cells, are presented. Finally, the putative toxicity of sepiolite and its advantages and perspectives for future prospects, such as the improvement of immunotherapy, are also discussed.

The stacking order of a bi-ionic K/Mg vermiculite from Malawi (Nyasaland), has been determined from Weissenberg data. The sample corresponds to a K/Mg interstratified vermiculite containing 50% K layers (dK = 1.01 nm) and 50% Mg layers with two layers of water (dMg = 1.44 nm). The observed intensities along (0, 0), (h, 0), (0, k) and (1, k) reciprocal rods were compared to the calculated intensities given by model defect structures. It was found that: 1) The (h, 0), (0, k) and (1, k) rods reveal the interstratification phenomenon which was previously observed on the (0, 0) rod; 2) The exchange of Mg by K does not occur randomly in a single interlayer, but occurs in interlayer domains sufficiently extensive to allow the reorganisation of the layer stacking and development of the ordered K-vermiculite structure from the semi-ordered structure characteristic of magnesium vermiculites; 3) For this sample, the interlayer water of the Mg phase occurs in two coexisting configurations; one configuration has water molecules forming octahedral coordination around the Mg2+, the other has water which is not linked to the Mg2+ cation forming two planes.

A lustrous appearance and interference-based colors make pearlescent pigments attractive for use in applications such as automotive paints, plastics, consumer electronics, and cosmetics. A combination of interference and absorption in the visible light spectrum improves significantly the hiding power as well as the color strength of pearlescent pigments while potentially extending their color range. The aim of the present study was to introduce synthetic fluorohectorites, having an appreciable diameter (~20 μm) and aspect ratio (~1000), as promising colored cores for pearlescent pigments. Fluorohectorites can adopt a variety of colors by ion-exchange reaction with cationic organic dyes of high absorption coefficient. Unlike related dye-exchanged natural montmorillonite clays, which undergo acid activation accompanied by release of dye at low pH, as is required for subsequent coating with TiO2 in an environment with low pH and elevated temperature, no leaching was observed with dye-exchanged synthetic fluorohectorites ([Na0.5]int.[Mg2.5Li0.5]oct.[Si4]tet.O10F2). Due to its significantly greater layer charge, more organic dye molecules were adsorbed per volume of the fluorohectorite than for montmorillonite. Consequently, the free volume available in the interlayer space for H3O+ diffusion was less for synthetic fluorohectorite than for montmorillonite. Acid attack via interlayer space was, therefore, retarded significantly for fluorohectorite. Acid attack from the external edges of synthetic fluorohectorites was in the range of conventionally applied mica pigment core (fluorophlogopite, ([K]int.[Mg3]oct.[AlSi3]tet.O10(F,OH)2) because of the comparable large diameter of the platelets. Montmorillonite, however, occurs with particle diameters typically <200 nm and the much increased relative contribution of edges to the total surface area also makes them more prone to acid attack and concomitant leaching. Aside from leaching stability, the confinement of organic dyes in the interlayer space restricts rotational and vibrational motions, which in turn stabilizes the dyes typically by ~100°C against thermal decomposition as compared to chloride salts of the dyes.

Dyestuffs and other reagents which exhibit characteristic colors when adsorbed on clay granules frequently have been employed as aids in clay identification. The colors generally are believed to result from pleochroic effects and acid-base or oxidation-reduction reaction mechanisms. Certain aniline dyes, solutions of which vary in color according to their hydrogen ion content, may be used to indicate the relative acidity of clay.surfaces as well as to heighten the natural pleochroism of kaolin minerals. When n clay sample has been pretreated with acid, the colors assumed by the adsorbed dye depend on the characteristic base exchange capacities of the various clay mineral groups present.

Aromatic diamines, amino phenols, and other compounds which can be oxidized to colored semiquinone cations permit particularly sensitive and positive identification of members of the montmorillonoid family and certain other three-layer clay minerals. Theories concerning the nature of this apparently catalytic oxidation on clay surfaces are inadequate to explain the reactions. New concepts and additional experimental information are needed.

Rehydroxylization of the anhydrous modification of dioctahedral montmorillonites can be carried out under DTA conditions with controlled atmosphere techniques. The structural character of the rehydrate prepared in this way is determined from X-ray and DTA data. The mechanism of the reactions by which the rehydrate can be formed is also considered. Thermal analysis curves of the rehydrate form of several pure mont-morillonite samples failed to show any large variation such as is shown by the curves of the original clays themselves. The possibility is considered that such large variations in the dehydroxylization curves of montmorillonites are related to structural instead of compositional variations within the sample. It is suggested that montmorillonites showing two reactions attributable to dehydroxylization may be mixtures of the rehydrate form and montmorillonite.

Changes in the infrared absorption spectrum of ammonium-saturated rectorite on heating suggest that the ammonium cations are hydrogen bonded to water molecules when the mineral is hydrated. Further spectral changes above 300°C indicate that lattice OH groups are perturbed by protons liberated from the decomposition of ammonium ions giving rise to an absorption doublet at 3500 and 3476 cm-1. The doublet attains maximal intensity when decomposition of ammonium cations and dehydroxylation of the mineral is complete at about 550°C.

The perturbation effect occurs only for swelling dioctahedral minerals which derive their layer charge from Al-for-Si substitution.

Sonic anisotropy of clay resulting from particle orientation was studied by means of velocity measurements on anisotropically consolidated kaolinite. Samples were prepared from a kaolin-water slurry under consolidation pressures ranging from 80 to 400 psi, with two distinct stress histories. Directional velocity measurements were made over a wide range of water contents as saturated samples were allowed to dry by evaporation to water contents below the shrinkage limit. Directional variation was most pronounced with partial saturation, when directional velocities differed by as much as a factor of two. The degree of sonic anisotropy is seen to correlate with variation in the shrinkage limit, showing a systematic dependence on particle orientation, but no unique relation to consolidation stress exists because of the overriding influence of stress history.