Se estudia la interacción del isocianato de butilo y del isocianato de fenilo con sepiolita, utilizando las técnicas de espectroscopía IR y anáilisis químico. En determinadas condiciones experimentales se produce un injerto de grupos orgánicos sobre la superficie mineral por formación de enlaces tipo uretano ≡ Si-O-CO-NH-R. Se ha puesto de manifiesto que el agua adsorbida sobre la superficie mineral, tiende a formar ureas simétricamente disustituídas como sub-producto de la reacción.

Clay mineral assemblages from a Quaternary sequence, sampled near the estuary of the Arno River, commonly contain some intergrade minerals, associated with other 14 Å phases and with illite and subordinate amounts of a kaolin mineral. The X-ray diffraction characteristics of such intergrade phases and their thermal modifications (100–600°C) are analysed and described.

The effectiveness of some chemical treatments for removal of interlayer material is investigated and the results discussed on the basis of X-ray diffraction pattern and C.E.C. changes. Finally the properties of these intergrades are compared with those of the 14 Å phases present in the sediments carried by the Arno River and its tributary the Era River as well as with those of a soil from the Era watershed. Hypotheses are expressed about the probable relationships between degree of chloritization and characteristics of the depositional environments.

Microprobe and atomic absorption analyses of large vermiculite crystals present in the upper horizon of a weathering profile on gabbro show that they differ appreciably in chemical composition. This together with the lack of any phyllosilicate precursor of comparable grain size, strongly suggests that the vermiculites were formed by precipitation of dissolved silicate matter, higher in the profile the vermiculite becomes unstable and is replaced by an Fe-rich smectite.

En el miembro basal de la Formación Utrillas, que aflora en las cercanias de Nuévalos, se ha localizado un nivel constituido por ilita, montmorillonita, natrojarosita, caolinita, cuarzo y materia carbonosa.

Se aportan datos de análisis químico, termodiferencial, termogravimetrico, microscopico y de difraccion de rayos X de la natrojarosita.

Se le atribuye a dicho sulfato un origen sedimentario por precipitación en un medio de aguas estancadas, desarrollado sobre materiales margo-yesiferos del Keuper. El hierro aportado al medio, la materia orgánica, y los iones procedentes de la disolución de las evaporitas Triasicas, provocaron las condiciones fisico-quimicas necesarias para la precipitación de la natrojarosita.

Los minerales de la arcilla son heredados, a excepcion de la montmorillonita que se la podria considerar paragenetica con la natrojarosita.

The adsorption of aniline (ANL) and p-chloroaniline (PCA) from 0·02 M methanol and chloroform solution on air-dried montmorillonite is determined by the conjunction of several factors: (i) basicity of the solute, (ii) complexing ability, Brönsted and Lewis acidity of the exchangeable cation, (iii) polarity and Lewis basicity of the solvent. The principal adsorption mechanisms, inferred from infrared data, are direct or indirect coordination and protonation of the adsorbate. They take place simultaneously and to a relative extent depending mainly on the exchange cation.

On Fe-, Al- and H(Al)-montmorillonite ANL and PCA give rise to type II complexes, characterised by an intense charge-transfer band in the infrared region and by the formation of radical cations, evidenced by ESR spectroscopy. This oxidation process occurs on heating in air, but with Fe3+ in vacuo also and even at ambient temperature in methanol solution. On Cu-montmorillonite ANL, contrary to PCA, does not give a type II complex; however, radical species are produced in air and in vacuo and their production is enhanced by heating.

Des zéolites de la famille Heulandite-Clinoptilolite se rencontrent dans toute la série cénomanienne littorale péri-armoricaine dans des faciès pétrographiques variés. Souvent présentes à l'étal de traces, leur abondance apparait liée à certaines conditions pétrogénétiques qui peuvent se réaliser localement à diverses périodes mais se généralisent au Cénomanien supérieur provoquant une régionalisation de la ‘paragenèse’: Clinoptilolite, Smectites, Cristobalite.

L'étude au microscope pétrographique et au microscope à balayage des échantillons les plus riches montre que la clinoptilolite se présente en cristaux automorphes dans des pores de dissolution intrasédimentaire. Son origine diagénétique est ici évidente; elle est postérieure à la dissolution des spicules de spongiaires et antérieure à la genèse de certaines sphérules de cristobalite. Ces néoformations se réalisent à partir des solutions interstitielles alimentées, au moins en partie, par l'altération de spicules de spongiaires, feldspaths détritiques, paillettes de mica, glauconie ...

L'origine détritique de la clinoptilolite des sédiments crétacés de la bordure occidentale du bassin de Paris qui avait été envisagée doit donc être écartée; deplús la paragenèse zéolitesmectites-cristobalite ne peut ici être utilisée comme l'indice d'une activité volcanique en cours de dépôt. Une partie des smectites, qui remplit certains pores de dissolution, prend également naissance par diagenèse précoce.

A synthetic dioctahedral vermiculite was saturated with Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and Ba, and examined by X-ray diffraction and infrared spectroscopy under various dehydration conditions. Cations which were larger than the ditrigonal hole (Cs, Rb, Ba) increased the b-dimension by forcing the oxygen triads open. With small cations the b-dimension decreased as a function of the residual water content rather than of cation size. The OH stretching vibration did not change in position, probably due to the inclined orientation of OH groups. The cations perturbed the lattice vibrations when they caused a change in the tetrahedral rotation angle, i.e. in b-dimension. With the small cations Be, Li and Mg, librations below 450 cm−1 shifted towards higher frequencies indicating cation migration into the empty octahedral sites.

Fe substitution for Al in kaolinite (from Venezuelan laterites) is proved by infrared spectroscopy and chemical techniques. The location of Fe in the octahedral sheet is characterized by two absorption bands, at 865–875 and 3607 cm−1, assigned as δ Al-OH-Fe and v OH respectively. The detection of the 865 cm−1 band requires the use of CsCl for the preparation of the disks heated to 270°C so that the clay delaminates as a result of a kaolinite-CsCl-H2O complex formation. The 3607 cm−1 absorption is detected when KI disks are prepared. These two characteristic frequencies persist after either thermal decomposition or selective chemical dissolution of free iron and aluminium hydroxides.

Selective chemical dissolutions by consecutive treatments for; (1) the removal of free iron oxides, (2) gibbsite removal and (3) extractions of Fe and Al from kaolinite, give additional evidence about the occurrence of this solid solution.

The distribution of rare earth elements (REE) in two different sediments, a marine clay and a till, was found to be dependent both on grain size and mineralogical composition. In the marine clay the REE content was highest in the coarsest fraction; in the till REE were markedly enriched in the finest fraction. Detrital and authigenic origins for different size fractions have been attributed on the basis of REE contents.