Clays, 509 base-poor

Note Base-rich and base-poor clays are clays rich or poor in adsorbed Ca h Mg-, Na, and K . 

Very acid clays, such as air-dried smectites with AF exchange ions, are equivalent in acidity to concentrated aqueous solutions of strong acids. Even very weak bases (poor proton acceptors) will protonate on such clay surfaces. For example, the amino form of 3-aminotriazole converts to the imino form on dry Mg +-montmorillonite (Russell et al., 1968a) ... 

The magnimde of the individual binary interaction parameters, efj, v j, i,j= 1, 2, must be computed from the two relations in Iiq. (14.5) with six parameters, of which only two (for the matrix, jj and Wjj) might be determined directly. The procedure developed for computation of the binary parameters in fully exfoliated PA-6-based CPNCs and in intercalated CPNCs based on PP and maleated polypropylene (PP-MA) have been published [Simha et al., 2001 Utracki et al., 2003 Utracki and Simha, 2004], but application of this strategy to a PS-based system needs to be examined. In the latter system, clay is poorly dispersed in PS, and beeause of... 

The incorporation of 5 % organically modified sepiolite, which is a microcrystalline-hydrated magnesium silicate, in a bisphenol A-based epoxy resin has no significant effect over the thermal stability of the epoxy resin, due to the poor dispersion of the clay and poor diffusion of the resin between fibres [69]. The effect of attapulgite (magnesium aluminium phyllosilicate) over the thermal properties of hyperbranched polyimides was studied. The presence of this silicate in the nanocomposites significantly improved the thermal stability of the neat polyimide [70]. 

Clay and shale are hydroaluminum silicates that by themselves do not add salts to the water that comes in contact with them. However, clay and shale often contain veins and nodules of gypsum, pyrite, and rock salt. Clay and shale are impermeable and form aquicludes rather than aquifers (sections 2.3 and 2.4), but because of the high solubility of gypsum and especially rock salt, groundwater in contact with clay and shale at the base of aquifers often gets saline and is of poor quality. 

Kaolin or china clay (RI 1.56) is hydrated aluminum silicates of very fine colloidal dimensions in the natural state. Clays are used in the paints because of their extremely good dispersibility in water-based systems, good suspension properties, and good brushability and opacity. However, they have poor weather resistance. 

Figure 7(b) shows a typical XRD pattern of oriented clay of odinite and verdine facies minerals. Since the sample was run in the air-dried state, the maximum expected spacing would be 15 A. The odinite spectra have a high background at low angles, a wide, poorly defined peak above 15 A in the air-dried state, and a wide, sharper but asymmetric peak near 7 A. The higher intensity is at 7.2 A. There is a lower intensity band near 7.5 A. The intensity of the total 7 A peak is low compared to the surface area of the wide band above 15 A. These features suggest that odinite is not simply a ferrous 7 A mineral based on a serpentine structure as defined in Bailey (1988). 

The focus of this paper is to review and identify those psychoactive plant species of sub-Saharan Africa. The biological and cultural diversity of Africa is immense (there are over 2,000 languages represented in sub-Saharan Africa). However, these ancient medicinal systems, usually based on oral traditions, are poorly documented even to this day. In contrast. North Africa and the Middle East have a relatively well documented traditional medicine (12-14). The Babylonians, Assyrians and Sumerians recorded heibal remedies in cuneiform on clay tables as long ago as 4000 BC. Not only can we attribute the origins of civilization to North Africa and the Middle East but also possibly the most important psychoactive plant, Papaver somniferum (opium poppy), from which the first alkaloid and psychoactive chemical was isolated. Morphine was first isolated by the German pharmacist Sertuner in 1803 (15). 

By contrast, smectite clays develop in poorly drained sites. On the basaltic island of Hawaii, soil clay mineral type changes in the sequence smectite-kaoli-nite-gibbsite as rainfall amount increases (Fig. 4.18). A similar, generalized zona-tion has been proposed for clay mineral distribution with depth in soils, again based on the degree of leaching (Fig. 4.19). 

Vertisols Old weathered soils with uniform, thick, clay-rich profiles. Deeply cracked and hummocky topography produced by intense seasonal drying of expandable clay minerals such as smectites. Soil profile poorly developed because of vertical mixing caused by the seasonal cracking. High in exchangeable cations (base-rich). 

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