Cation and anion salts

Demineralizers are often used to treat raw makeup water or condensate where high purity is required, such as in large central station boHers that operate at high steam pressures. Demineralizers employ a combination of cation and anion exchange to remove additional material, including sodium and ammonium cations. VirtuaHy aH salt anions, such as bicarbonate, sulfate, and chloride, are removed and replaced by hydroxide ions in the demineralizer. 

Electrodialysis. Electro dialysis processes transfer ions of dissolved salts across membranes, leaving purified water behind. Ion movement is induced by direct current electrical fields. A negative electrode (cathode) attracts cations, and a positive electrode (anode) attracts anions. Systems are compartmentalized in stacks by alternating cation and anion transfer membranes. Alternating compartments carry concentrated brine and purified permeate. Typically, 40—60% of dissolved ions are removed or rejected. Further improvement in water quaUty is obtained by staging (operation of stacks in series). ED processes do not remove particulate contaminants or weakly ionized contaminants, such as siUca. 

The methods for naming cations and anions may be combined to name zwitterions the cationic center is cited before the anionic center, both in the replacement prefixes and in the suffixes, e.g. (204). One should be aware, however, that Chemical Abstracts names zwitterions by an extraordinary circumlocution, in which water is hypothetically added and then hypothetically taken away, to give names consisting of four separate words ending in inner salt, e.g. (205). 

The mobilities of ions in molten salts, as reflected in their electrical conductivities, are an order of magnitude larger than Arose in Are conesponding solids. A typical value for diffusion coefficient of cations in molten salts is about 5 X lO cm s which is about one hundred times higher Aran in the solid near the melting point. The diffusion coefficients of cation and anion appear to be about the same in Are alkali halides, wiAr the cation being about 30% higher tlrair Are anion in the carbonates and nitrates. 

The drermodynamic data for CuaS-FeS (Krivsky and Schuhmann, 1957) show that drese sulphides mix to form approximately ideal ionic liquids. These are molten salts in which the heat of mixing is essentially zero, and die entropy of mixing is related to the ionic fractions of die cations and anions. In the present case die ionic fractions yield values for the activities of the two sulphides... 

Salt effects on the reaction of 2,4-dinitrochlorobenzene with amines or alkoxides have been investigated.Reinheimer et al. have studied decelerative ion pairing of alkali metal methoxides in reaction with this substrate cations and anions in added salts have specific effects on ion pairing. 

The synthesis of ionic liquids can generally be split into two sections the formation of the desired cation, and anion exchange where necessary to form the desired product (demonstrated for ammonium salts in Scheme 2.1-1). 

The influence of the nature of cations and anions on the solubility characteristics of the resulting salts with organic substrates is also discussed in Section 5.3.4. It has... 

A salt is an ionic solid containing a cation other than H+ and an anion other than OH or O2-. When a salt such as NaCl, K2CO3, or A1(N03)3 dissolves in water, the cation and anion separate from one another. 

If you know how the cation and anion of a salt affect the pH of water, it is a relatively simple matter to decide what the net effect will be (Example 13.12). 

Strategy First, decide what ions are present in the solution. Then classify each cation and anion as acidic, basic, or neutral, using Table 13.5. Finally, consider the combined effects of the two ions in each salt. 

If the ammonium salt is present with other cations and anions, a titrimetric procedure (see Chapter 10) is usually employed,... 

The commonly used method for the determination of association constants is by conductivity measurements on symmetrical electrolytes at low salt concentrations. The evaluation may advantageously be based on the low-concentration chemical model (lcCM), which is a Hamiltonian model at the McMillan-Mayer level including short-range nonelectrostatic interactions of cations and anions [89]. It is a feature of the lcCM that the association constants do not depend on the physical... 

The process of ionization in water of an electrolyte or a salt, whereby cations and anions are formed. 

The packing arrangement of cation and anion in diazonium salts has important implications not only for the structure of diazonium ions, as discussed above, but also for the solid-state chemistry of these compounds, in particular with regard to halogeno-de-diazoniations such as the Schiemann reaction. TWo of the papers of Gougoutas (1978, with Johnson, and 1979) contain, in addition to the X-ray analyses, experimental results on bromo- and iodo-de-diazoniation, which can be interpreted on the basis of the structural information (see Secs. 10.4-10.6). 

FIGURE C.3 An ionic solid consists of an array of cations and anions stacked together. This illustration shows the arrangement of sodium cations (Na+) and chlorine anions (chloride ions, Cl-) in a crystal of sodium chloride (common table salt). The faces of the crystal are where the stacks of ions come to an end. 

In an ionic solid, the coordination number means the number of ions of opposite charge immediately surrounding a specific ion. In the rock-salt structure, the coordination numbers of the cations and the anions are both 6, and the structure overall is described as having (6,6)-coordination. In this notation, the first number is the cation coordination number and the second is that of the anion. The rock-salt structure is found for a number of other minerals having ions of the same charge number, including KBr, Rbl, MgO, CaO, and AgCl. It is common whenever the cations and anions have very different radii, in which case the smaller cations can fit into the octahedral holes in a face-centered cubic array of anions. The radius ratio, p (rho), which is defined as... 

For cations 74-75 (Fig. 27), low temperature NMR experiments were necessary to reveal stereodynamical behaviors and allow the observation of split signals for the enantiomers [38,144]. Stereoselective recognition between the chiral cations and anions was observed in essentially all cases as integration of the split signals revealed the preferential occurrence of one diastereomeric salt over the other. 

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