Vermicular glaucony grains observed by transmission electron microscopy (TEM) show three irregularly alternating zones. Zone A has a high degree of linear orientation, no void space, and relatively defect-free lattice-fringe images. Zone B has an amalgamated bundle texture with a sub-parallel, linear orientation of bundles to each other and to zone A. Zone B has little or no void space, and lattice images appear to be a combination of those typical of zone C with minor amounts of modified zone A forms. Zone C has a randomly oriented, curved, and circular or semicircular bundle texture. In addition, zone C has much void space and curvilinear and linear lattice-fringe images with numerous defects, including edge dislocations. Such morphologic and crystallographic characteristics indicate that zones B and C probably comprise the glauconitic minerals of the vermicular glaucony grains, and that zone A comprises non-glauconitic micaceous minerals of higher structural order. Zone B is sharply demarcated from zone A, but B zone bundle textures merge gradationally to those of zone C. These spatial relationships suggest that zone B forms first on the surface of zone A. Sub-parallel orientation in the B zone could be produced by initial confinement between adjacent A zones. Once constraints change or are removed, the randomly oriented, curved, and semicircular or circular bundles of zone C develop.

The sedimentation behavior of a fine kaolinite, comprising a substantial proportion of colloidal particles as well as non-colloidal ones, has been studied when fresh FeCl3 or F2(SO4)3 electrolytes are added. The sedimentation behavior depends on the pH and the nature of electrolytes and can be explained qualitatively, in our study, by the theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO theory). Fe helps also to aggregate the kaolinite particles in flocs. Two extreme kinds of qualitative sedimentation have been observed: flocculation-sedimentation and accumulation-sedimentation. However, the transition between the two kinds of sedimentation is quite progressive. The present results are discussed in reference to the DLVO theory and the hydrolysis behavior of Fe electrolytes.

The colloidal state (stable, coagulated, or gel-like) and the rheological properties of Na-rich montmorillonite (Wyoming) dispersions are strongly influenced by organic cations. This effect is shown for homologous organic cations: alkyl trimethylammonium ions, paraquat, diquat, alkyl bispyridinium ions, and the triphenylmethane dyes crystal violet, methyl green, and tris (tri-methylammonium phenyl) methane chloride. The critical coagulation concentrations, cK, are small (often < 1 mmol/L) because the cations are enriched in the Stern layer and influence the solvent structure near the surface. The strong adsorption of the counterions at the clay-mineral surface causes cK values to increase with the solid content. Charge reversal (recharging) of the particles was observed with the longer chain alkyl trimethyl-ammonium ions, dodecyl bispyridinium ions, and crystal violet. Other cations reduced the electrophoretic mobility to zero but positive particle charges were not observed.

The plastic viscosity increased sharply at the critical coagulation concentration and showed a minimum slightly below cK, which was caused by the electroviscous effect. Yield values were developed at concentrations above cK. In most cases, yield values reached a plateau where the amount of organic cations was ∼0.5 mmol/g, i.e., about half of the cation-exchange capacity. The cK values decreased with increasing hydrophobicity of homologous compounds, but the yield value showed maxima at intermediate chain lengths. The yield value of several 0.5% dispersions was high, e.g., dodecyl trimethylammonium ions, 71 Pa; paraquat, 100 Pa; diquat, 42 Pa; hexyl bispyridinium ions, 53 Pa (vs. Ca2+, 0.2 Pa; Al3+, 0.7 Pa). The storage modulus as a function of the number of organic cations changed in a similar way as the yield value, and high values were observed (e.g., dodecyl trimethylammonium ions, hexyl bispyridinium ions: 1000 Pa, paraquat: >4000 Pa). Thus, dispersions with high viscosity, yield value, and pronounced viscoelasticity are obtained by coagulating Na-rich montmorillonite dispersions with organic cations.

I was a delicate child, and to my great embarrassment I was excused from gymnastics as a teenager owing to an illness whose identity is still mystery, at least to me. That is when I acquired my world-weariness, a permanent and invincible lethargy that was to get worse with the passing years. Tiredness as a natural state has for many years been a recurring theme, when I'm complaining about life in letters and conversation. My friends consider it a bad habit of mine, almost an attempt to attract attention, and they don't take me seriously. “I'm increasingly falling apart”, I recently told an old friend. He replied with a slightly mocking air: “You've been telling me that for twenty years”. But the truth is - and it is difficult to explain this to anyone younger - that the descent into the void is long, much longer than I would have ever imagined, and slow, so slow as to appear almost imperceptible (although not to me). The descent is continuous and, what is worse, irreversible: you descend one step at a time, but having put your foot on the lower step, you know that you will never return to the higher one. I have no idea how many more downward steps are to follow. I can only be sure that their number is steadily decreasing.

Solutions containing hydroxy-FeAl oligocations (HFA) were prepared by two procedures: (1) treatment of a mixture of FeCl3 and AlCl3 with aqueous Na2CO3, followed by aging of the product and (2) preliminary preparation and aging of hydroxy-Al13 oligocations followed by reaction of the latter with aqueous FeCl3. Ion-exchange of Na-montmorillonite with HFA yield pillared clay (designated as FeAl-PILC) with d(001) values of 1.98–1.56 nm and a surface area of 230 m2/g. The pillar structure, thermal stability, surface acidity, and reduction behavior of the pillared clays were determined by 27Al-NMR, XRD, DTA, Mössbauer spectroscopy, Py-IR, TPD, TPR. Fe/Al ratios greatly affect the pillar structure, surface area and thermal stability of FeAl-PILC. The pillar in FeAl-PILC with Fe/Al ratio <0.5 has a Keggin structure, similar to that of Al-PILC, but the pillar structures of FeAl-PILC with Fe/Al ≥0.5 are the ferric tripolymer species similar to those of Fe-PILC. The basal spacings, surface area, and thermal stability are decreased with increasing Fe/Al ratio. There is relatively strong interaction between Fe and Al in the pillars. The interaction is enhanced with decreasing Fe/Al ratio. Reduction of the Fe phase in FeAl-PILC was reduced by the interaction of Fe with Al.

Nowadays there is a paradox ruling utopia. The place for the ‘spirit of youth’ in our society, apart from the traditional age groups, ought to mean a strong upswell of utopian projects, since youth is the age for questioning the world as it is, and idealistically rebuilding the future. And yet there is a paralysis of optimistic imagination as to the future. It is the unpredictability of the future, in a world that makes creating the new in every field its very driver, that makes any imaginings about a future society so perilous and uncertain. However, the demand for diversity and the aesthetic dimension are two factors that could characterize the contemporary vision, in contrast to the old austere utopias that are now bankrupt.

I should like to consider both the relationship between the authorities and society in the theme of ecology, and its chronology.

As far as chronology is concerned, it seems to me that concern for the environment started to emerge in the USSR, at least on a large scale, mainly during the Brezhnev years (1964-1982).

X-ray diffraction of four natural samples of ferrihydrite indicates the presence of crystalline domains within the primary particles. The average diameter of the primary particles (determined from low-angle powder patterns) decreases from 4.1 nm to 2.5 nm as the domain size in the xy-plane (determined by applying the Scherrer equation to the broad [110] XRD peak at 0.26–0.27 nm) decreases from 1.0 nm to 0.77 nm. The Si content (measured by acid-oxalate extraction) increases from 4.1% to 6.1% as both the domain and particle sizes decrease; other factors, however, are likely to be important in influencing particle size. For one sample of ferrihydrite, the smallest possible domain (i.e., c = 0.94 nm in the z-direction) contains 36 O atoms and three Si atoms. A model for ferrihydrite is suggested in which silicate bonds to, and bridges, the surfaces of the domains. The model can account for several aspects of the behavior of siliceous ferrihydrites.

What does “encyclopedic knowledge” mean to us today? I believe that, as in the eighteenth and nineteenth centuries, what we mean by this term is a knowledge that strives to embrace in detail the greatest possible number of sciences and bodies of knowledge. As Sainte-Beuve said in 1850 regarding Madame de Genlis:

The very name of Bihar, a district in the eastern part of India, evokes images of anarchy, banditry, and disarray. Already traversed by distinct cultural zones - Bhojpuri, Mithila, Magadha, and the tribal zone of Jharkhand - Bihari society is characterized by bloody clan conflict over territorial rights. The doggedness with which the region's protagonists form militias is a perpetual source of front-page news. Pitted against the Brahmans and Bhumihar Rajputs, the large landowners, are the herding and soldier castes such as the livestock-herding Yadavas, the farming Kurmis, and the former saltpeter miners, the Noniyas, whose economic, social, and political growth has given them real power. And although Magadha's rich Buddhist past attracts pilgrims and tourists, and Mithila's beautiful painted murals and villages draw art connoisseurs, Bihar ranks as one of the least safe regions of India. The rate of banditry and other crime reaches surprising levels.

Ten years ago, an issue of the journal L'Homme et la Société was entitled “La Mode des identités.” Most of the articles were about cultural identity, but the basic thrust of the work was “a critique of the ‘fashion’ of identity calling into question the validity of a notion as striking as it is uncertain.” Recently, a special issue of the journal Sciences Humaines, entitled “Identité et identités,” dealt with personal, familial, social, professional identities and only spoke of cultural identity marginally and in a roundabout way. Finally, in a manual of Sociologie politique published by the Presses Universitaires de France, the author takes to task the notion of ethnicity inherent to cultural identity and pushes the critique of the ethnic group to the point of negating its objective existence. Must we think then that the notion of cultural identity is henceforth obsolete, that it has lost all pertinence?

The influence of surfactants on the flow behavior of sodium montmorillonite dispersions (2% w/w) was studied for a cationic (cetylpyridinium chloride, CPCl) and an anionic surfactant (sodium dodecylsulfate, SDS). When the dispersion pHs were >3.5 and <7, CPCl concentrations >10−4 M increased the shear stress but the Bingham yield value remained virtually unchanged (τo ≈ 100 mPa). At pH ≈ 7, the shear stress and yield point decreased with increasing CPCl concentration (τo from 430 to 100 mPa). The flow properties of sodium calcium bentonite dispersions were independent of pH and CPCl concentrations ≤ 10−4 M; they increased modestly at higher concentrations. At pH < 4, SDS addition to the sodium montmorillonite dispersions increased the shear stress and yield value to a maximum value (τo = 2100 mPa) at 10−3 M SDS; higher SDS concentrations reduced the shear stress and yield value. At pH > 4, the flow values decreased to a minimum value at 10−2 M SDS (τo from 430 to 50 mPa). The flow of the sodium calcium bentonite dispersions at pH > 4 was independent of SDS concentrations ≤ 10−3 mole/liter; at higher SDS concentrations, the flow values increased more strongly in sodium calcium bentonite than in sodium montmorillonite dispersions.

Surfactants influence the flow behavior of sodium montmorillonite dispersions by their action on the card-house networks in strongly acidic medium and, at higher pH, by the electroviscous effect. At the highest surfactant concentrations without flocculation, the shear stress and yield value are increased by interacting chains of opposed particles.

Addition of the surfactants increases the salt (NaCl) stability of the dispersions because the adsorbed surface active agents influence the counterion distribution between the Stern and the diffuse ionic layer.

For more than forty years, Diogenes has been striving, with the limited resources at its disposal, to mark the progress of the human sciences around the world. The journal emerged from the encounter between an institution and a person. The institution was the Conseil international de la philosophie et des sciences humaines (CIPSH) that was founded under the auspices and on the initiative of UNESCO with the aim of regrouping a variety of different international associations in the field of Geisteswissenschaften; the person was Roger Caillois, then an international civil servant with UNESCO. The CIPSH wanted to equip itself with an organ of international scholarly communication that was capable of serving as a bond and link between its various member associations.

Highly tectonized contact between serpentinite and younger pegmatite in the magnesite mine of Wiry contains various layer silicates. Vermiculite, chlorite, smectite, and interstratified mica-vermiculite were recognized by means of routine XRD examination. Two three component interstratifications of mica-vermiculite-chlorite and chlorite-swelling chlorite-smectite were identified by a combined procedure of deconvolution of the XRD patterns and simulation of XRD tracings. A mineral with large diffraction maxima, displaying “chlorite intergrade” characteristics, appeared to be a mixture of chlorite, mixed layer chlorite-smectite, and vermiculite. Polytypes of phyllosilicates were determined by the X-ray transmission method. Due to the heritage of parent mineral polytype structure by transitional products of alteration, two distinct sequences of layer silicates were observed: one formed from trioctahedral mica (vermiculite, mixed layer mica-vermiculite); and one evolved from chlorite (e.g., mixed layer chlorite-swelling chloritesmectite). A tentative scheme of the primary contact zone structure, not obscured by subsequent brittle tectonics either by transformation of layer silicates, is proposed.

Why do we learn some lessons more easily than others - indeed with alacrity and enthusiasm? Often these are not of the most attractive sort. It seems so frequently as if there is a sheer perversity in us.

NEXAFS is shown to be an excellent technique, of potentially widespread application, for the determination of the orientation of organic molecules intercalated in preferentially oriented thin films of polycrystalline, layered minerals. A NEXAFS study of [Mg2Al(OH)6]+C7H5O2 · nH2O, a layered anionic clay, is described. This material shows a transition from a layer spacing of 15.4 Å to only 9 Å at a remarkably low temperature (below 100°C). This is shown to be accompanied by a change in the angle of the plane of the benzoate molecule to the 00ℓ planes from 35° ± 10° to 0° ± 10°. The tilt of the benzoate anion in the room temperature structure demonstrates the presence of an interaction between the phenyl ring and the positively charged, brucite-like layers. Furthermore it is suggestive of the importance of hydrogen bonding in determining the interlayer spacing and stability.

Chlorite minerals, found in a great variety of rocks and geological environments, display a wide range of chemical compositions and a variety of polytypes, which reflect the physicochemical conditions under which they formed. Of particular importance for studies dealing with ore deposit genesis, metamorphism, hydrothermal alteration or diagenesis is the paleotemperature of chlorite crystallization. However, in order to understand the relationship between chlorite composition and formation temperature and hence use chlorite as a geothermometer, one must determine how other parameters influence chlorite composition. These parameters may include fO2 and pH of the solution and Fe/(Fe + Mg) and bulk mineral composition of the host rock.

Four approaches to chlorite geothermometry, one structural and three compositional, have been proposed in the past: 1) a polytype method based on the (largely qualitative) observation that structural changes in chlorite may be partly temperature-dependent (Hayes, 1970); 2) an empirical calibration between the tetrahedral aluminum occupancy in chlorites and measured temperature in geothermal systems (Cathelineau, 1988), which has subsequently been modified by several workers; 3) a six-component chlorite solid solution model based upon equilibrium between chlorite and an aqueous solution, which uses thermodynamic properties calibrated with data from geothermal and hydrothermal systems (Walshe, 1986); and 4) a theoretical method based on the intersection of chlorite-carbonate reactions and the CO2-H2O miscibility surface in temperature-XCO2 space, which requires that the composition of a coexisting carbonate phase (dolomite, ankerite, Fe-calcite or siderite) be known or estimated (Hutcheon, 1990). These four approaches are reviewed and the different calculation methods for the compositional geothermometers are applied to a selection of chlorite analyses from the literature. Results of this comparative exercise indicate that no single chlorite geothermometer performs satisfactorily over the whole range of natural conditions (different temperatures, coexisting assemblages, Fe/(Fe + Mg), fO2, etc.). Therefore, chlorite geothermometry should be used with caution and only in combination with alternative methods of estimating paleotemperatures.