Cation exchange capacity—See

Chlorites have rather low specific surface areas and cation exchange capacities (see Chapter 3, section 3.2), a result of the blockage of the interlayer regions by hydroxy sheets, and do not expand at all in water. Exchangeable cations are likely to be found only on external surfaces and edges of chlorite particles. 

Metameric Colours. Colours that appear to be the same under one type of illuminant but, because they have different spectral reflectivity curves, will not match under a different illuminant. Two white vitreous enamels may be metameric, for example, if one is opacified with titania in the anatase form whereas the other contains titania in the form of rutile. Methuselah. A 9-quart wine bottle. Methylene Blue Index A simple approximate method for assessing the surface area of a clay. O.OIM methylene blue dye is added to aqueous suspension of clay, in successive small amounts, to determine the least amount of dye required to impart colour to the water suspending the clay. Dye up to this amount is absorbed by the clay, so that this is a measure of the clay s cation exchange capacity (see ionic exchange). For most pottery clays this is proportional to the surface area to a good approximation. ASTM C837 specifies a test for clays. 

Under saturated or very wet conditions, soils tend to have increased amounts of OM. This results in dark colors and dramatically changes the chemical characteristics of a soil. OM increases a soil s sorptive and cation exchange capacities and thus alters the movement and extraction of components present. OM increases ped formation and stability, thus increasing both aeration and percolation, but under saturated conditions, reduction reactions prevail (see Figure 2.12). 

The sorption behavior of 11 PAH compounds (a training set, Table 11) on various solid phases (e.g., three soils and two sediments) with different properties to relevant sorption (e.g., organic carbon content, clay content, pH, cation exchange capacity CEC Table 12), was determined by batch equilibrium studies [1]. Batch equilibrium tests were designed to determine rates of equilibrium sorption under conditions of high mixing and high surface areas of the solid particles (see Chap. 3). 

Fig. 4.21 Idealized soil profile showing master soil horizons and horizon abbreviations. The 0, A, E and B master horizons can be further subdivided into subordinate horizons depending on composition (see Figs 4.23M-.25). Note that the O horizon is composed of fresh (L) and partially decomposed (F) organic litter. Soil profiles are typically 0.5-1.0m thick such that master horizons are typically centimetres to tens of centimetres thick. SOM, soil organic matter CEC, cation exchange capacity.

Fig. 3-154. Separation of heavy and transition metals on an ion exchanger with both anion and cation exchange capacity. — Separator column IonPac CS5 eluent 0.006 mol/L pyridine-2,6-dicar-boxylic acid, pH 4.8 with LiOH flow rate 1 mL/min detection see Fig. 3-152 injection volume 50 pL solute concentration 1 ppm Fe3+ and Cu2+, 3 ppm Ni2+, 4 ppm Zn2+, 2 ppm Co2+, and 3 ppm Fe2+.

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