Exchangeable sodium

Usually, a series of standard NaCl solution is prepared containing 0.1-0.5 meq/1 Na by dilution from 0.05(N) NaCl solution using saturated calcium sulphate solution in place of water. Since mostly the calcium in soil extract is associated with sulphate these solutions contains about 30 meq/1 calcium as sulphate. Next to this, the flamephotometer is calibrated with pure NaCl standard and subsequently the standard containing the calcium sulphate is sprayed and any interference effect due to calcium is measured. 

However, sodium may be determined also by atomic absorption spectrophotometry using emission mode. Calcium does not normally interfere in this technique. 

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Selective absorption of durene from heavy gasoline (bp 150—225°C) is possible using a version of UOP s Sorbex technology where the X zeoHte is made selective for durene by replacing the exchangeable sodium cations with lithium ions (16). 

Sodium-proton exchanger Sodium-proton antiport... 

This is defined as the relative concentration of sodium to calcium plus magnesium, and is represented by a parameter known as the sodium adsorption ratio (SAR). The absolute concentration values of the different cations in irrigation water are not adequate for estimating probable hazards. An important consideration is the extent to which the exchangeable sodium percentage (ESP) of the soil will increase as a result of adsorption of sodium from the irrigation water. The higher the ratio, the... 

Table 2 Relative tolerance of selected crops to exchangeable sodium [12]...

Soils properties are very sensitive to the type of exchangeable ions. Calcium imparts favorable physical properties to the soil, while adsorbed sodium causes clay dispersion and swelling. It is generally recognized that an exchangeable sodium percentage of 10 is sufficient to cause soil dispersion, reduction of soil permeability and impaired growth of some crop plants. On the other hand, excess salt concentration prevents the dispersive effect of adsorbed sodium. 

FIGURE 26.1 Cation exchanger (sodium salt form) two-dimensional scheme. 

Some zeolites have the ability to exchange sodium for calcium and thereby function as water softeners by removing Ca2+. After the zeolite has become saturated with Ca2+, it can be renewed by washing it in a concentrated NaCl solution to restore the Na+ ions. Zeolites are also used to prepare ion exchange resins, as molecular sieves and as catalysts. 

The lifetime of a zeolitic alkylation catalyst depends on the concentration of Brpnsted acid sites. This has been shown by Nivarthy et al. (78), who used a series of zeolites H-BEA with varied concentrations of back-exchanged sodium ions. The sodium decreased the concentration of Brpnsted acid centers, which led to a concomitant decrease in the measured catalyst lifetime during alkylation. 

F5. Flear, C. T., Cawley, R, Quinton, A., and Cooke, W. T., The simultaneous determination of total exchangeable sodium and potassium and its significance, with particular reference to congestive cardiac failure and the steatorrhea syndrome. Clin. Sci. 17, 81-104 (1958). 

Fig. 8.26 Exchangeable sodium percentage (ESP) along a Burleson soil column, as a function of the sodium adsorption ratio (SAR) of irrigation water. The values were obtained by percolating the soil columns with sodic water (total electrolyte concentration of 11 meq/L). Each curve corresponds to a given applied volume of solution (Thomas and Yaron 1968)...

Blower, C. J., Smith, T. D. The gas-phase decomposition of nitromethane over metal ion-exchanged sodium Y zeolite and sodium X zeolite. Zeolites, 1993, Volume 13, Issue 5, 394-398. 

When carbonic anhydrase inhibitors block the enzyme in the kidney, HjCOj formation— and consequently the availability of H3O+ (i.e., protons)—decreases. Since the Na+ ions in the filtrate cannot be exchanged, sodium is excreted, together with large amounts of water, as a result of ion hydration and osmotic effects. The result is diuresis, accompanied by a dramatic increase in urine volume. There is also failure to remove HCOj" ions because there is no H3O+ to form HjCOj, which would decompose to COj -1- HjO. Therefore, the normally slightly acidic urine becomes alkaline. The strong carbonic anhydrase inhibitors also increase K+ excretion, an undesirable effect. 

Sodium ion exchange. Sodium ion exchange on zeolites (Section 7.3) or on synthetic organic cation-exchange resins such as Dowex-50 (a sulfonated polystyrene Fig. 14.1), in most circumstances, is superior to the above softening methods.13 The exchange process favors binding of Ca2+ or Mg2+ over Na+ in the solid resin phase ... 

Digitoxin and its derivatives bind to the sodium-potassium pump and prevent it from exchanging sodium and potassium ions. When given in small quantities the result, especially in cardiac tissue, is that calcium ion content will be upset and calcium will be liberated from its stores. The newly available calcium can then interact with cardiac muscle protein to cause contraction. This is a therapeutic effect for those suffering from insufficient heart-pumping action (congestive heart failure or dropsy). The heart is made to contract efficiently and forcefully (inotropic effect). However, you can see that there may be a fine line between a necessary contraction and one which... 

Na 2.58 y P e" 1.39 23Na(n,y)24Na Exchangeable sodium measurements... 

Figure 10.17 Flow schematic of electrodialysis systems used to exchange target ions in the feed solution, (a) An all-cation exchange membrane stack to exchange sodium ions for calcium ions in water softening, (b) An all-anion exchange membrane stack to exchange hydroxyl ions for citrate ions in deacidification of fruit juice...

Ammonium zeolites are transformed into acid zeolites by the decomposition of ammonium cations the zeolite is modified to its acid form by exchanging sodium or any other charge-balancing cation present in the zeolite for ammonium, as follows [18] ... 

The sulfonated polystyrene beads can be used as a cation exchange resin. For example, if the sulfonated resin is treated with sodium hydroxide, the sodium salt of each of the sulfonic acid groups is formed. This resin can then be employed to exchange sodium cations for other cations in an aqueous solution. 

Figure 4.26. Relationship between SAR and exchangeable sodium ration (ExNa/ExCa1/2 or ExNa/ExMgj/2 for soil minerals under different pH values (data taken from Fletcher et al., 1984).

Theoretically, a plot of S AR versus ExNa/ExCa1/2 or exchangeable sodium ratio (ESR) will produce a straight line with slope equal to KQ. The average magnitude of KG for soils of the arid west is approximately 0.015 (mmol L 1) 1/2. However, the experimental Kg appears to be dependent on pH, salt concentration, and clay mineralogy. Furthermore, the experimental KG does not appear to be constant across the various sodium loads. Commonly, as sodium load increases, KG also increases. Furthermore, as pH increases, KG decreases (Fig. 4.26). 

TABLE 10.1. Sodium Adsorption Ratio (SAR) and Exchangeable Sodium Percentage (ESP) Values Associated with 20% Reduction in Saturated Hydraulic Conductivity (SHC) for Pembroke Soil (10- to 30-cm Incremental Depth) at Three pH Values... 

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