Encarnación Gámiz

Assessment of two Spanish bentonites for pharmaceutical uses

Abstract Two Spanish bentonites have been studied for possible pharmaceutical use, following U.S. Pharmacopoeia (1990) and B. Pharmacopoeia (1988) trials and other methods such as elementary chemical analysis, ion exchange analysis, specific surface analysis, etc. Bentonite 1 did well in nearly all trials. It is sample with a high clay content, being more than 90% smectite (saponite). It is therefore potentially suitable; however, it exhibits an unsuitable content of coarse particles, organic matter and loss on drying. Bentonite 2 fails some U.S.P. trials. It is a raw sample that will require pretreatment and purification. It has a great potential because, from a mineralogical point of view, the finest particles reach a high level of purity in smectite (84%) and its chemical composition indicates that it is a montmorillonite, more suitable for pharmaceutical use than other minerals of the same group.

Chemical, mineralogical and (micro)morphological study of coarse fragments in Mediterranean Red Soils

Abstract We studied the gravels derived from mica schists and micaceous quartzites of three Mediterranean Red Soils (Haploxeralf and Cryoboralf) from the Sierra Nevada (Andalusia, Spain) with emphasis on the following aspects: morphology (visual evidence of weathering, thin section description and scanning electron microscopy); composition (X-ray diffraction, extractable Fe, Al and Si, and electron microprobe analysis); and chemistry (pH, cation exchange capacity, specific surface area and organic carbon content). The gravels had undergone considerable modification during weathering in soil. A loss of the primary rock structure was detected, together with a decrease in compactness, an increase in roundness, color value and chroma. Neoformed kaolinite was present and relatively high contents of extractable forms of iron, aluminium and silica (citrate–dithionite and oxalate) were detected. From an analytical point of view, the surface properties (CEC and SSA) increased and the equilibrium pH decreased in the clasts which had undergone most weathering. The SEM study shows that the fabric changes from laminar schistose in the parent rock to other types in the gravels due to the weathering process. Electron microprobe analysis revealed the presence of phyllosilicates together with iron oxides in the illuvial infilling materials of fissures in the most altered clasts. These infillings affect the properties of the coarse fragments. The relationship detected between the properties of fine earth and those of the gravel fractions suggest that the coarse fragments have a significant influence on the properties of the soil.

Whiteness of talcum powders as a quality index for pharmaceutical uses

Talc is a whitish raw material of mineral origin

Are Mediterranean mountains Entisols weakly developed? The case of Orthents from Sierra Nevada (Southern Spain)

Two Orthents from Sierra Nevada National Park (Spain), classified as loamy-skeletal mesic Typic Xerorthent and loamyskeletal frigid Lithic Cryorthent were studied. They were situated at 1460 and 2000 m, derived from micaschists and quartzites under Mediterranean mountain climate conditions with mesic and cryic temperature regimes and xeric moisture regime. These Orthents are weakly developed, as shown by their reduced thickness, their lack of diagnostics subsurface horizons, sandy loam textures, skeletal, and lithochromic colors. Quartz is present in significant amounts, particularly in the fine light sand fraction. Analysis of the quartz grains of the fine light sand by scanning electron microscope (SEM) and backscattered electron images (BSE) revealed the presence of significant physical and chemical alteration features such as fractures, corrosion gulfs, fields of etch pits and dissolution of intergranular surfaces. This process is confirmed by electron microprobe analysis (EMPA) since the edges of the quartz grains have a higher proportion of cations other than Si, compared to their centre. Further evidence indicates the authigenic nature of the process. Starting from quartz etching an assessment of soil weathering has been made (W index from Marcelino et al. (1999). The alteration of the quartz, together with the development of a ultramicrofabric with several fabric units (investigated with SEM), and other characteristics (mineralogical, chemical, etc.) are considered indicative of some pedogenic evolution. These facts are especially interesting in the case of weakly developed Mediterranean mountain soils from Sierra Nevada, where processes of chemical weathering have traditionally not been considered very active. D 2003 Elsevier B.V. All rights reserved.