Adsorption-desorption of Cd to Ca montmorillonite (SAz-1) was studied at concentrations ranging from 44.5 to 266.8 μM. An adsorption model was employed in the analysis of the data. The procedure consists of solving the electrostatic Gouy-Chapman equations and calculating adsorbed amounts of the cations as the sum of the cations residing in the double-layer region, and the cations chemically bound to the surface, in a closed system. The model also accounts explicitly for cation complexation in solution. The model yields good predictions for the adsorbed amounts of Cd, Ca and Mg, by employing binding coefficients from previous studies for the divalent cations and for Na, K and CdCl+. The model calculations also yield good predictions for the apparent hysteresis observed in the adsorbed amounts of Cd after each of 3 cycles of desorption. The apparent hysteresis is explained by the reduction in the total concentrations of Ca and Mg in desorption cycles, and the corresponding increase in the magnitude of the surface potential. Our estimates indicate that adsorption of Cd is mostly to planar, rather than edge sites of the clay mineral.

The illitic end of mixed-layer illite-smectite series (I/S) in shales from Lower Cretaceous Barra de Itiúba Formation, Sergipe-Alagoas basin, was examined with X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). A mathematical decomposition of XRD patterns shows different I/S and illite populations. All the samples contain ordered (R = 1) I/S, poorly crystallized illite (PCI) and well crystallized illite (WCI). A randomly interstratified (R = 0) I/S was also identified in a fractured zone at 1020 m. The percentage of expandable layers in ordered I/S decrease progressively from 20% to 10%. TEM observations show a continuous change in morphology between two basic particle shapes: elongated (lath) and isometric. The size and morphology of particles change with increasing depth. The proportion of laths decreases while isometric particles become predominant. However, both particle types continuously grow and enrich the larger size fraction. The growth process is driven by a mass transfer from the dissolving small particles of predominantly I/S (R = 1) composition to the larger (more illitic) lath and isometric ones. The proportion of lath-shaped particles decreases with depth indicating that the more stable population upon increased burial is the isometric well crystallized illite (WCI) particles. Very large laths are observed in the fault zone where conditions may favor faster growth processes.

The reaction of hydroxy-Al interlayers in montmorillonite with monosilicic acid was studied by chemical analysis, X-ray diffractometry (XRD), and Fourier-transform infrared (FTIR) spectroscopy. Hydroxy-Al interlayers in montmorillonite was prepared by treating Ca-montmorillonite (<2) μm) with hydroxy-Al solutions at an initial Al concentration of 0.5 mM and OH/Al molar ratios of 1.0, 2.0, and 2.5. The resultant partially interlayered montmorillonite was reacted with 0.5, 0.9, and 1.4 mM monosilicic acid solutions.

A substantial amount of monosilicic acid was adsorbed by the interlayer hydroxy-Al polymers through the reaction of Si-OH groups with mainly Al-OH groups, resulting in the formation of silicated Al-interlayers with Si/Al molar ratios up to 0.19. The adsorption of silicic acid by interlayer hydroxy-Al polymers increased the basal spacings of the partially interlayered montmorillonite. This effect was most pronounced for the hydroxy-Al interlayered montmorillonite formed in the systems at an OH/Al ratio of 2.0, in which the d(001) reflections (110°C) shifted from 13.6 Å before silication to 14.1 Å with a shoulder at 17.0 Å after silication. The differential IR spectrum of the silicated hydroxy-Al interlayers in montmorillonite exhibited absorption bands at 935 and 3730 cm−1, which can be assigned to Si-O and Si-OH, respectively, of the adsorbed Si(OH)4. An interlayer structure analogous to that of “proto-imogolite” was, thus, proposed for the silicated interlayer hydroxy-Al polymers in montmorillonite. This study revealed a new mechanism through which Si enters the interlayer spaces of smectite. The silication of hydroxy-Al-interlayered clays in natural environments and the related modifications in surface properties of the clays should receive increasing attention.

Ammonium-saponite is hydrothermally grown at temperatures below 300°C from a gel with an overall composition corresponding to (NH4)0.6Mg3Si3.4Al0.6O10(OH)2. The synthetic saponite and coexisting fluid have been characterized by means of X-ray powder diffraction, X-ray fluorescence, Induced Coupled Plasma-Atomic Emission Spectroscopy, thermogravimetric analysis, transmission electron microscopy, CEC determination using an ammonia selective electrode, and pH measurement. In the crystallization model developed, crystallization started with the growth of individual tetrahedral layers with an aluminum substitution not controlled by the A1IV/A1VI ratio in the gel and hydrothermal fluid, on which the octahedral Mg layers can grow. During the synthesis, individual sheets stacked to form thicker flakes while lateral growth also took place. The remaining A1VI partly replaced ammonium as the interlayer cation.

Culture is determined by a historical, that is, a temporal perspective, and by another that is atemporal, the transcendental scale of values. Diversity, within the limits of a certain harmony that embraces the whole, is an enriching factor far more than one tending to dispersal or division. The ancient Egyptian and Coptic, Muslim and modern heritage in Egypt and black Africa, as well as the Assyrians’, Phoenicians’, Berbers’, and then the legacy from black Africa coming from Mesopotamia, the Levant, North Africa, Sudan and Somalia respectively, are contributing to the emergence of a new though historical humanism. The author takes the view that the Arab mentality, contrary to a common and widely held belief, is nourished by a pluralism that is both surprising and stimulating.

The response of two swelling clays (SWy-1 and SAz-1) and of one non-swelling clay (KGa-1) and of a series of mixtures of these clays to different electrolyte concentrations was examined using clay-modified electrode techniques. A non-interacting probe ion, Fe(CN)63−, was monitored via reduction for its arrival at a Pt electrode coated with thin films of the clay mixtures. The three clays had both different temporal responses and different equilibrium currents. For SWy-1 the currents were developed over time and were dependent upon the electrolyte of the bathing solution, which was consistent with X-ray diffraction data literature for the interlayer dimension. Similar behavior was found for SAz-1, but for KGa-1, currents were instantaneous and were independent of the bathing electrolyte. This suggests that the pores controlling the probe ion transport were between particle or pinhole in nature. When mixtures of the clays were examined, it was found that KGa-1 caused defects within the structures of the mixed clay films. The SWy-1 mixture was not as affected by these disruptions as was the SAz-1 mixture.

The structure of the interlayer cation-water system in La-vermiculite with a unit cell of a = 5.33(5), b = 9.18(6), c = 15.13(9) Å and β = 96.82(7)° has been determined in space group C2/m. Under ambient conditions, the interlayer La cations are distributed on a 3a × b superlattice which disappears on dehydration but returns on rehydration. The basal spacing does not change during the dehydration/rehydration process. The character of the superlattice spots indicate that the cation-water system, at ambient conditions, is ordered over relatively large domains. The La cations are surrounded by 8 neighboring water molecules in a distorted cubic arrangement. The spaces between the La-water clusters are occupied by triads of water molecules that are relatively mobile.

An inquiry into the rhetorical aspects of history may seem paradoxical, given that historical discourse is not typically included among those types which, since Aristotle, have been understood to be governed by rhetoric; these types being the deliberative council, the tribunal and the commemorative assembly. It was to these specific audiences that the three kinds of discourse—the deliberative, judiciary, and panegyric—were addressed. However, are the boundaries of the historian's audience sufficiently delineated in order to allow us to identify it as a specific addressee? This first objection, which regards the very legitimacy of the subject of these remarks, can be met by noting a common trait that links history to the above-mentioned three types of discourse; that is, competition between opposed discourses requiring a choice. In each case the aim is to structure a debate that calls for a clear-cut decision. Yet a major problem of the discipline of history is that it allows both for widely varying descriptions of the same series of events, and sanctions the use of a variety of equally acceptable rules or preferences for interpreting a given slice of the past.

Tetramethylphosphonium-smectite (TMP-clay) and tetramethylammonium-smectite (TMA-clay), were prepared and characterized as adsorbents for a series of aromatic and chlorinated hydrocarbons. The sorption of benzene, alkylbenzenes, and carbon tetrachloride as vapors and as solutes from water was studied to evaluate the effect of water on adsorption efficiency. Adsorption of organic vapors depended on the N2 BET surface area. TMA-clay was a slightly better adsorbent than TMP-clay, due to its somewhat higher surface area. The Langumir isotherms obtained indicated that adsorption occurred predominantly in the interlayer micropores, apparently on mineral surfaces between onium ions. Adsorption efficiency of both organo-clays decreased, compared to vapor sorptions, in presence of water. Lower sorption was apparently due to shrinkage of the interlayer pore or cavity sizes by hydration of interlayer TMA and TMP cations. Although sorption efficiencies of both organo-clays was reduced in presence of bulk water, the extent of reduction was much less for TMP-clay. Thus, TMP-clay was a better adsorbent than TMA-clay in presence of water, despite its lower surface area, in direct contrast to vapor sorption. The Langumir isotherms indicated interlayer sorption of benzene, alkylbenzenes and carbon tetrachloride from water by TMP-clay. The absence of Langumir isotherms for toluene, ethylbenzene and p-xylene uptake from water by TMA-clay indicated that these bulkier solutes were not adsorbed in the interlayers. These results indicate that hydration of TMA cations causes shrinkage of the interlayer pores to dimensions that exclude these solutes. The lower degree of hydration of TMP cations enables TMP-clay to maintain interlayer pores large enough to accommodate the bulkier alkylbenzenes.

Tsvetan Todorov, in his book Us and Them. French Thinking on Human Diversity, asked the following question: “How does one, how should one relate to those who do not belong to the same community as we do?” This question has been posed somewhat differently by intellectuals of the Americas anxious to develop paradigms of identity that will contribute to the successful construction of a society whose aim is to integrate heterogeneous ethnic groups: “How does one, how should one relate to those who are members of our new society but who live either on its margins or who are frequently considered as different?” The mixed-race (métissage) approach, applied to the Latin Americas situation, was in part a response to this question. Here the “us” did not designate metropolitan Europeans engaged in thinking about the “others,” that is to say non-Europeans, but Latin Americans thinking about relations among various dominant groups and the varying “others” within their own society, since the “others” were part of “us.” The meaning of “us” is equally problematic when applied to North America. “What happens when words like ‘community’ and ‘us’ cease to have the clear and immediate meaning that Todorov seems to ascribe to them?” Sherry Simon recently asked. Although offering a general critique of the monological conception of culture and identity – a critique based on Bakhtin's work on polyphony and dialogism, on James Snead's investigation of the hybrid nature of several texts belonging to the European canon (such as The Odyssey and The Divine Comedy), and on the studies of Angelo Ara and Claudio Magris in regard to the heterogeneity of Trieste – she nevertheless begins her essay on a personal note, describing life in the multicultural city of Montreal, where “many children come out of mixed or immigrant marriages, some going to French schools, some to English,” and who can not “define themselves as products of a single culture” (pp. 15-16). Although I agree with Sherry Simon that the “us” of culture is never a given (it should be mentioned that Todorov himself writes that we must “give up basing our thinking on such a distinction” [between us and them] p. 421), it is essential here to emphasize the special ambiguity of the conception of “us” in the ex-colonies of the New World, where the “collision of cultures” implied not only, on the one hand, a confrontation among Spanish, Portuguese, British, and French colonists, but also between the colonists and the African slaves as well as with the immigrants who arrived after independence. Todorov's conception of nationhood (p. 422) as “a more or less perfect (although never total) coincidence of a State and a culture” - which he toned down a bit by adding that a culture is often identified with a particular region, a group of countries, or even a stratum of the population (pp. 424-425) - is even less applicable to the new societies of America than it is to Europe. Not only are we talking about hybrid societies (and what society isn't, to some degree?), but of societies conceived as hybrid, either multicultural (Canada) or mixed-race (Latin America). If, as Ernest Renan insisted at the end of the XIXth century, the idea of the modern nation is based on a conscious disregard for our diverse ethnic origins, the concepts of identity of the societies of the New World have often been based on an explicit symbolization of their heterogeneity.

Kaolinite:NaCl intercalates with basal layer dimensions of 0.95 and 1.25 nm have been prepared by direct reaction of saturated aqueous NaCl solution with well-crystallized source clay KGa-1. The intercalates and their thermal decomposition products have been studied by XRD, solid-state 23Na, 27Al, and 29Si MAS NMR, and FTIR. Intercalate yield is enhanced by dry grinding of kaolinite with NaCl prior to intercalation. The layered structure survives dehydroxylation of the kaolinite at 500°–600°C and persists to above 800°C with a resultant tetrahedral aluminosilicate framework. Excess NaCl can be readily removed by rinsing with water, producing an XRD “amorphous” material. Upon heating at 900°C this material converts to a well-crystallized framework aluminosilicate closely related to low-carnegieite, NaAlSiO4, some 350°C below its stability field. Reaction mechanisms are discussed and structural models proposed for each of these novel materials.

Whatever our profession we are all engulfed in daily life and in the obscurity and density of the mental world. Who is this “I” that finds expression in such a wide variety of societies, in the convictions of the group and temperament of the individual self, in all that I perceive imperfectly and that makes me me? What does this sometimes slippery, sometimes thorny “I” say about the various attitudes towards knowing: the things I desperately want to know, things I believe myself capable of dispensing with, those I fear knowing?

The swelling of some well-defined Mg-, Ca-, Sr- and Ba- homoionic montmorillonites was studied in the domain of water relative pressures lower than 0.95. This involves the expansion of the crystal lattice itself, commonly known as the “interlamellar expansion” or “inner crystalline swelling”. The initial freeze-dried clays were characterized by nitrogen adsorption-desorption volumetry and controlled transformation rate thermal analysis. The evolution of the structural and textural properties of these different clays at different stages of hydration and dehydration was investigated using water adsorption gravimetry, immersion microcalorimetry at different precoverage water vapor relative pressures and X-raydiffraction (XRD) under controlled humidity conditions. Large textural variations are observed in the dry state depending on the exchangeable cations. The 2-layer hydrate exhibits the most ordered layer stacking. Water is mainly adsorbed in the interlamellar space. With increasing water pressure, each homoionic species leads to a 1-layer hydrate and, with the exception of Ba-montmorillonite, to a predominant 2-layer hydrate. The relative pressure corresponding to the formation of the 2-layer hydrate decreases with increasing hydration energy of the interlayer cation. For Ca-, Sr- or Mg-montmoriHonites, simulation of XRD patterns leads to the definition of successive homogeneous states corresponding to the 2-layer hydrate. Furthermore, it yields the water filling ratio corresponding to the different hydration states during adsorption and desorption of water vapor.

Two series of pillared clays were prepared from a purified montmorillonite (95%) from La Serrata of Nijar, Spain, and polycations of Al and Zr using various methods. The effect of both the pillaring cation and the procedure of preparation on the physicochemical characteristics of the resulting materials was studied. Changes in texture were determined by X-ray diffraction (XRD) and N2 adsorption at 76 K and changes in acidity were determined by thermogravimetry following pyridine adsorption at room temperature and further desorption at a constant heating rate of 10 K min−1 in the range of 298–623 K. The relation between the size and charge (n/q) of the pillaring cation, which is dependent on the degree of cation hydrolysis, is the main factor affecting pore size and acidity of the synthesized materials. The pH of the pillaring solution affects the stability of the parent clay and the properties of the pillared clay. Below a pH of 3 and depending on contact time, the montmorillonite may delaminate and partially dissolve to produce products that affect the properties of the resulting materials. Microporosity increases for both Al or Zr-pillared clays. For Zr-pillared clays, microporosity is accompanied by changes in the mesoporosity and macroporosity as a result of clay delamination. Acidity dramatically increases by pillaring, especially strong acidity, and the acid strength distribution depends on starting salt concentration, aging time, and temperature.

The bonding in a cronstedtite layer was studied using a ninefold ordered supercell band structure calculation. The tight-binding scheme based upon the extended Hückel method was used to predict the electronic structure. The size of the problem was 162 atoms with 798 valence orbitals. The calculation showed different orbital interactions of oxygen p-orbitals with neighboring atoms with respect to the position in the layer. Substitution of Fe for Si in the terahedra reduced the role of the valence p-orbitals of the central Fe atoms. The d-orbitals of Fe were split in accordance with the rule of t2g-eg splitting. Although the density of states at the Fermi level was high, the partially filled 3d-bands were too narrow to permit normal metallic conduction.

This inquiry will be limited to an analysis of Turkic borrowings that have been attested in inscriptions found in Mongolia and southern Siberia in the period beginning around the year 700 A.D., as well as in Turkic-Uighur manuscripts, beginning around the year 900 A.D., conserved in northern Tarim (especially in the Turfan region) and in Dunhuang, which is a Chinese outpost on the main road of the silk trade. We will look only at borrowings that predate Islamization, a process that developed rapidly during the eleventh century and of which some borrowings are still part of the language of the Islamic Turkish world. Although most of our study will concentrate on pre-Islamic borrowings that were fully assimilated into written words, we will will also investigate some transcriptions of foreign terms that are mentioned in various manuscripts of a theological bent (most notably of Indian, Iranian, Chinese, and Syriac origin and found in Buddhist, Manichaean, and Nestorian Christian texts) as well as words of a very technical nature. We will also look at more contemporary terms that are derived from several major semantic fields.

Daniele Hervieu-Léger and Marcel Gauchet explain that today the hold that the religious dimension has always exerted over human societies is, of very recent date but definitely, slackening; that it is becoming ‘hollow’ and ceases to inspire collective action, leaving henceforth wide open the question of knowing in which name we should attempt to take our destiny in our hands and base the norms of collective being. This question at once summons up another, implicitly contained in the latter: is every ethical norm (or moral norm, for we are not making a distinction between the two concepts here) ultimately religious in origin, as is most often supposed, or can one in fact conceive of sketching the outlines of a moral code that is immanent within the social relationship, a moral code that is sufficiently coherent and self-consistent to do without, at least in theory, a religious-type transcendence? Here, I should like to make a case for the second response by emphasizing that religion - whatever meaning one bestows on this notion, still undefined today - does not constitute the primary, irreducible social and historical fact that is most often supposed, but that it should itself be interpreted as the formulation of a more original and more universal formulation: the threefold obligation of giving, receiving, and repaying distinguished by Marcel Mauss in his famous Essay on the Gift. Of course, I shall not claim here to do more than sketch a few possible lines of argument. But even before formulating them, I must call to mind two prejudicial objections that my argument has encountered.

Complex X-ray diffraction (XRD) profiles are described crystallographically by simulating XRD peaks for each phase, and adding the various elementary patterns to fit the experimental X-ray pattern. X-ray patterns of a ground muscovite and three polyphasic diagenetic I/S samples are fitted with this powerful, but time-consuming, technique. In the 6°–10°2θ CuKα range, the asymmetry of the muscovite peak is related to a very broad coherent scattering domain size (CSDS) distribution; for the I/S samples the even greater asymmetry is due to the presence of several phases with close, but distinct crystallographic characteristics (I/S, illite, and detrital mica).

A simulation-decomposition approach for modelling XRD patterns is introduced to describe quickly and accurately the various clay minerals (essentially mixed-layer illite/smectite and illite) present in a sedimentary series, and to follow their individual evolution during diagenesis. The theory for these simulations is described briefly. The influence of mixed-layer heterogeneity (the distribution of CSDS, and the distribution of smectite content) on the shape of X-ray peaks is shown theoretically to be minimal. Indeed, for both CSDS and smectite content, the important parameter for peak shape appears to be the mean value of the distribution and not its width and/or its shape. The theoretical limitations of the decomposition method are presented. Minor experimental limitations (reproducibility, experimental peak shape, discrimination) make this method a powerful and reliable tool to describe X-ray patterns. The method is used to show the simultaneous occurrence of three “illitic” phases in a sedimentary series from the Paris Basin. The respective evolution of the three phases is clearly evidenced by using this decomposition method. However, the precise identification of these different phases remains difficult to determine because of the difference in peak width between simulated and experimental X-ray patterns.

Transmission X-ray diffraction (XRD) of C6–16 alkylammonium ion-exchanged montmorillonite SAz-1 with Ag-behenate as an internal standard provided accurate estimates of d(001) values of the alkylammonium ion-exchanged montmorillonite. Inspection of d(001) values were made to assess the possible formation of gauche conformers (alternate arrangements of the molecules) in the interlayer and to determine the critical carbon chain length, nC. Using conventional constraints for nC(I′) and nC(II) equal to 1.36 and 1.77 nm, respectively, provided ambiguous nC(I′) and nC(II) values. The dependence of full-width at half-maximum values on nC allowed better estimates of nC(I′) and nC(II) because “integral” and “non-integral” peak characteristics relating to interstratification could be included in the assessment.

The effect of inaccurate estimates of nC(I′) and nC(II) values on calculated interlayer cation exchange capacity (Ci) using two conventional concepts of calculation were compared. It was found that a procedure based on the summation of fractions of the layer charge gave relative errors of Ci <2%, even where the number of carbon atoms corresponding to both nC(I′) and nC(II) differed by ± 1 nC from the correct values. This method of calculation of Ci is recommended when reliable values of Ci are needed.