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preface to fifteenth edition

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11.38 SECTION 11<br />

TABLE 11.18<br />

Relative Selectivity of Various Counter Anions<br />

Counterion<br />

Relative<br />

selectivity for<br />

Dowex 1-X8 resin<br />

Relative<br />

selectivity for<br />

Dowex 2-X8 resin<br />

OH 1.0 1.0<br />

Benzenesulfonate 500 75<br />

Salicylate 450 65<br />

Citrate 220 23<br />

I 175 17<br />

Phenate 110 27<br />

<br />

HSO 4 85 15<br />

<br />

ClO 3 74 12<br />

<br />

NO 3 65 8<br />

Br 50 6<br />

CN 28 3<br />

<br />

HSO 3 27 3<br />

<br />

BrO 3 27 3<br />

<br />

NO 2 24 3<br />

Cl 22 2.3<br />

<br />

ClO 4 20<br />

SCN 8.0<br />

<br />

HCO 3 6.0 1.2<br />

<br />

IO 3 5.5 0.5<br />

HPO 2 4 <br />

5.0 0.5<br />

Formate 4.6 0.5<br />

Acetate 3.2 0.5<br />

Propanoate 2.6 0.3<br />

F 1.6 0.3<br />

exchange behavior of a cation because they do not take account of the influence of the aqueous<br />

phase. More specific information about the behavior <strong>to</strong> be expected from a cation in a column elution<br />

experiment is given by the equilibrium distribution coefficient K d .<br />

The partitioning of the potassium ion between the resin and solution phases is described by the<br />

concentration distribution ratio, D c :<br />

(D ) c K<br />

<br />

[K ] r<br />

<br />

[K ]<br />

Combining the equations for the selectivity coefficient and for D c :<br />

(D ) k<br />

<br />

[H ] r<br />

[H ]<br />

c K K/H <br />

The foregoing equation reveals that essentially the concentration distribution ratio for trace concentrations<br />

of an exchanging ion is independent of the respective solution of that ion and that the uptake<br />

of each trace ion by the resin is directly proportional <strong>to</strong> its solution concentration. However, the

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