For potassium-exchanged

Figure 2.9. Schematic diagram of AG versus reaction coordinate for potassium exchange on a Matapeake soil where AG is the Gibbs free energy. [From Sparks and Jardine (1981), with permission.]...

Ogwada, R. A. and D. L. Sparks, 1986a. Use of mole or equivalent fractions in determining thermodynamic parameters for potassium exchange in soils. Soil Sci. 141 268-273. 

Although ion-exchange is most often thought of in terms of surface as described above, it can also apply to exchange of ions from within a phase, as in the use of zeolites in water softening, or sodium for potassium exchange when K-feldspar is altered to albite at high temperatures. 

Potassium fluoride [7789-23-3], KF, is the most frequently used of the alkaU metal fluorides, although reactivity of the alkaU fluorides is in the order CsF > RbF > KF > NaF > LiF (6). The preference for KF is based on cost and availabiUty traded off against relative reactivity. In its anhydrous form it can be used to convert alkyl haUdes and sulfonyl haUdes to the fluorides. The versatility makes it suitable for halogen exchange in various functional organic compounds like alcohols, acids and esters (7). For example, 2,2-difluoroethanol [359-13-7] can be made as shown in equation 9 and methyl difluoroacetate [433-53 ] as in equation 10. 

Polymer-supported tetraphenylphosphonium bromide is a recyclable catalyst for halogen-exchange reactions. The reaction of 1 equivalent of chloro-2,4-dinitrobenzene with 1 5 equivalents of spray-dned potassium fluoride and 0.1 equivalent of this catalyst in acetonitnle at 80 C for 12 h gives 2,4-dinitro-fluorobenzene m 98% yield An 11% yield is obtained without the catalyst [3 /]. 

Kinetic data" for the exchange of benzyl iodide and potassium iodide... 

Radenti et al. reported the corrosion rate of a typical potassium chloride fluid of 247 mils/year at 212°F. In contrast, they found by substituting potassium carbonate for potassium chloride, the corrosion rate was reduced to 3 mils/year t10 . Unfortunately, potassium carbonate is not optimum as a drilling fluid additive because it can produce massive amounts of calcium precipitation, may elevate the pH to undesirable levels, and in all cases reduces the calcium ion concentration to such a low level as to promote destabililzing cation exchange with clay minerals. 

In the case of ion-exchange, a selective carrier (e.g. valinomycin for potassium) extracts the cation into the polymer layer (Figure 5 and Tablel 1). 

Figure 11.2. Top shows exchange of higher valent iron for lower valent potassium when sodium and iron are at the same concentrations. Bottom shows exchange of sodium for potassium when sodium is at a much higher concentration than iron or potassium. The common anions in soil, chloride, sulfate, nitrate, carbonate, bicarbonate, and the anions of small acids such as acetate, have been omitted for clarity. 

TABLE VI. InK values and site group capacities (meq 100/g) for simulating the Cs Ca equilibria at 25°6 of potassium-exchanged Camp Berteau montmorillonite subjected to alternate wettingdrying cycles... 

Bychkova and Shvarev [16] recently prepared nanosensors (0.2-20 pm) for sodium, potassium and calcium using the precipitation method. Similarly to the previous works, the plasticized poly(vinyl chloride) included a phenoxazine chro-moionophore, a lipophilic ion exchanger and a cation-selective ionophore. The dynamic range of the very selective sensors was 5 x 10 4-0.5 M for sodium, 1 x 10 5-0.1 M for potassium and 2 x 10 4 - 0.05 M for calcium. As was demonstrated by Bakker and co-workers [45] a particle caster can be used can be used for preparation of much larger beads (011 pm). 

Only few data are available for this kind of analysis. In addition to the above-presented data, exchange isotherms have been measured for Th and for -zeolite An experimental result for potassium zeolite L suspended in water and exchanged at room temperature with is shown in Fig. 6. For... 

Suzuki et al. [90] developed a diffuse refleetanee flow-through sensor for improving selectivity in the determination of lithium in human fluids, where sodium can occur at concentrations up to 10 000 times higher than that of the analyte. The mechanism on which the sensor action relies (Fig. 5.21.2) was previously exploited by the authors to develop a probe-type sensor for potassium [91]. The sensor response is based on an A -H exchange according to... 

Mechanism of Action An ion exchange resin that releases sodium ions in exchange primarily for potassium ions. Therapeutic Effect Moves potassium from the blood into the intestine so it can be expelled from the body. 

Carbonic anhydrase influences the tubular reabsorption of sodium in proximal tubule where biocarbonate absorption occurs and in the distal tubule where sodium is exchanged for potassium or hydrogen ion and bicarbonate is formed as the accompanying anion. The hydration of carbon dioxide takes place under the influence of enzyme carbonic anhydrase which forms carbonic acid which dissociates and breaks into hydrogen and carbonate ions. 

Silver(I) fluoride dispersed on the surface of calcium fluoride demonstrates improved fluoride nucleophilicity for halogen exchange. Silver(I) fluoride/calcium fluoride is considerably more active than potassium or cesium fluoride dispersed on the surface of calcium fluoride.38... 

Newly fermented wines are usually supersaturated with potassium bitartrate. Wineries routinely remove the excess potassium bitartrate in wines by refrigeration or ion exchange procedures. These steps are necessary to obtain a wine free of tartrate deposits after bottling. Calcium may also combine with tartrates which contribute to the deposits in wines. Generally, the stabilization practices for potassium bitartrate are sufficient to remove calcium tartrate from wines. 

A barium hydroxide adduct of amylose was prepared by Senti and Witnauer07 by means of an exchange of barium hydroxide for potassium hydroxide in a potassium hydroxide-amylose adduct however, the exact... 

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