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Cation-exchange capacity is measured by displacing all the bound cations with a concentrated solution of another cation, and then measuring either the displaced cations or the amount of added cation that is retained. [1] Barium (Ba 2+) and ammonium (NH 4 +) are frequently used as exchanger cations, although many other methods are available. [4] [5]
Print/export Download as PDF; ... base saturation refers to the fraction of exchangeable cations that are base cations.
Stilbite shows a wide variation in exchangeable cations: silicon and aluminium ions occupy equivalent sites and can substitute for each other. Since silicon and aluminium have a different charge (Si 4+ and Al 3+ ) the ions occupying the sodium/calcium site have to adjust to maintain charge balance.
Laboratory tests used to diagnose a soil as dispersive focus on the cation exchange capacity of a soil sample and its cation breakdown. Soil cations are dominated by Ca 2+, Mg 2+, K +, and Na +, as well as H + in acidic soils. The exchangeable sodium percentage ( "ESP", (sodium / (total cations)) * 100 ) is a key indicator derived from these ...
CEC is the amount of exchangeable hydrogen cations (H +) that will combine with 100 grams dry weight of soil and whose measure is one milliequivalent per 100 grams of soil (1 meq/100 g). Hydrogen ions have a single charge and one-thousandth of a gram of hydrogen ions per 100 grams dry soil gives a measure of one milliequivalent of hydrogen ion.
An advantage of this method is that exchangeable cations can be removed by passing a chloride solution through the plate once the sample has been dried. Exchanging cations can be useful when establishing peaks for standards with variable interlayer cations. For example, nontronite has an interlayer which can contain both calcium and sodium. If ...
Montmorillonite is a subclass of smectite, a 2:1 phyllosilicate mineral characterized as having greater than 50% octahedral charge; its cation exchange capacity is due to isomorphous substitution of Mg for Al in the central alumina plane. The substitution of lower valence cations in such instances leaves the nearby oxygen atoms with a net ...
Exchangeable cations are present in the clay minerals interlayers and on the external basal planes of clay platelets. Cations also compensate the negative charges on the clay particle edges caused by the protolysis of silanol and aluminol groups ( pH dependent charges).