Univalent cations

Complex salts of thorium fluorides have been generated by interaction of ThF with fluoride salts of aLkaU or other univalent cations under molten salt conditions. The general forms of these complexes are [ThF ] [15891 -02-8] ThFJ [1730048-0] and [ThF ] [56141-64-1], where typical countercations are LC, Na", K", Cs", NH" 4, and N2H" 3. Additional information on thorium fluorides can be found in the Hterature (81). 

TBT exists in solution as a large univalent cation and forms a neutral complex with CH or OH . It is extremely surface active and so is readily adsorbed onto suspended particulate material. Such adsorption and deposition to the sediments limits its lifetime in the water column. Degradation, via photochemical reactions... 

Glass electrodes are responsive to univalent cations. The selectivity for these cations is achieved by varying the composition of a thin ion-sensitive glass membrane. 

Since the repulsive forces are determined by the true sizes of ions, and not their crystal radii, the radius ratios to be used in this connection are the ratios of the univalent cation radii to univalent anion radii.12 Values of this ratio for small ions are given in Table II, together with predicted and observed coordination numbers, the agreement between which is excellent. 

Abstract Inorganic polysulfide anions and the related radical anions S play an important role in the redox reactions of elemental sulfur and therefore also in the geobio chemical sulfur cycle. This chapter describes the preparation of the solid polysulfides with up to eight sulfur atoms and univalent cations, as well as their solid state structures, vibrational spectra and their behavior in aqueous and non-aqueous solutions. In addition, the highly colored and reactive radical anions S with n = 2, 3, and 6 are discussed, some of which exist in equilibrium with the corresponding diamagnetic dianions. 

Sulfur-Rich Polysulfides with Complex Univalent Cations. 132... 

Table 2 Structure data of sulfur-rich polysulfides with univalent cations (for abbreviations, see text)... 

For Raman spectra of hexa- [30, 40] and heptasulfides [46] with complex univalent cations, see the original literature. 

For chemical and electrostatic reasons, some ions are bound more strongly than others. Polyvalent cations are much more strongly bound than univalent cations the same holds for anions. Thus, when a solution containing Ca ions (hard water) is passed through a cation exchanger which is present in its Na or H+ form, the Ca ions are held back in it and the Na or H+ ions leave instead. Similarly, an anion exchanger in the OH form will retain Cl or SO ions from the solution. By a cation and anion exchanger in series, the former in the H+ and the latter in the OH... 

On the assumption that = 2, the theoretical values of the ion solvation energy were shown to agree well with the experimental values for univalent cations and anions in various solvents (e.g., 1,1- and 1,2-dichloroethane, tetrahydrofuran, 1,2-dimethoxyethane, ammonia, acetone, acetonitrile, nitromethane, 1-propanol, ethanol, methanol, and water). Abraham et al. [16,17] proposed an extended model in which the local solvent layer was further divided into two layers of different dielectric constants. The nonlocal electrostatic theory [9,11,12] was also presented, in which the permittivity of a medium was assumed to change continuously with the electric field around an ion. Combined with the above-mentioned Uhlig formula, it was successfully employed to elucidate the ion transfer energy at the nitrobenzene-water and 1,2-dichloroethane-water interfaces. 

In the simple case of a diffusible, univalent cation B+ and anion A- and non-diffusible anion X present in phase 2, the condition of electroneutrality gives... 

As the membrane has a surface charge leading to formation of a diffuse electrical layer, the adsorption of ions on the BLM is affected by the potential difference in the diffuse layer on both outer sides of the membrane 02 (the term surface potential is often used for this value in biophysics). Figure 6.12 depicts the distribution of the electric potential in the membrane and its vicinity. It will be assumed that the concentration c of the transferred univalent cation is identical on both sides of the membrane and that adsorption obeys a linear isotherm. Its velocity on the p side of the membrane (see scheme 6.1.1) is then... 

By measuring the distribution coefficient, K, of cationic radon on Nafion resin (H+ form) in BrF -trichlorotrifluoroethane solutions as a function of the concentration of BrF, we have been able to show that the charge on the radon cation is +2 and that the parent molecule is RnF2 This physico-chemical method makes use of the fact that BrF produces the univalent cation BrF2, which competes with Rnz for sites on the resin. The following equilibria occur in this system (R represents the anion of the resin) ... 

From Section 19-1, we learned that if the concentrations of the weak acid or base and its salt are 0.05 Mor greater, and the salt contains a univalent cation, then... 

The pH optimum of both exopectate lyases lies in the alkaline region. The pH optimum of exopectate lyase of Erwinia aroideae is influenced by univalent cations. The enzyme activated by K+ and NH4+ has its pH optimum at 8.0, but, in the presence of Na+ ions, it is shifted towards the alkaline region. 

Where only univalent cations are considered, the activities calculated by Equations 9.27 and 9.28 are equivalent in value, but this is not the case if divalent ions are included. The reaction describing exchange of sodium for calcium ions,... 

In a solution containing a crown ether (Cr) and a salt of a univalent cation (MX), the equilibria (1) can exist. Dlp and Z>C8lp are the dissociation constants... 

Some caution is required when comparing the association constants obtained from extraction experiments with those measured under anhydrous, homogeneous conditions. Iwachido et al. (1976, 1977) have shown that the extracted cation retains part of its aqueous solvation shell on complexation. In particular, the small univalent cations (Li+, Na+) and bivalent cations give high hydration numbers for their crown-ether complexes. Water molecules completing the co-ordination sphere of the cation have frequently been encountered in the solid state of crown-ether complexes (Bush and Truter, 1970, 1971). The effect of small amounts of water on the equilibria (1) has not been studied yet for crown ethers. However, it has been found that the presence... 

The nature of the surface of alumina is important in its application as an adsorbent for chromatography. This subject is covered by special literature. Inorganic ions can be separated on alumina as well as on silica (241). Anions are adsorbed together with bivalent cations, but not together with univalent cations indicating, again, equimolecular... 

Suppose the researcher involved with the sodium ion concentration study of Sections 15.1 and 15.2 becomes interested in the wine-making process we have been discussing in Sections 15.3 and 15.4. In particular, let us assume the researcher is interested in determining the effects on the percent alcohol response of adding 10 milligrams of three different univalent cations (Li, Na, and K ) and 10 milligrams... 

Figure 15.17 Factor combinations for the randomized complete block design investigating two qualitative factors, type of univalent cation and type of divalent cation. Each factor combination is replicated.

Experiment Univalent cation Divalent cation % Alcohol... 

Because nominal factors are not continuous, we cannot use a linear model such as yu = Po + Pi- i/ + P2 2/ + 1/ to describe the behavior of this system. For example, if a , were to represent the factor univalent cation , what value would x, take when Li was used Or Na Or K There is no rational basis for assigning numerical values to Xj, so we must abandon the familiar linear models containing continuous (quantitative) factors. 

Note that for the randomized complete block design, there is no covariance between the effects of the univalent cations and the effects of the divalent cations. 

For the example used in Section 15.5, there would be three y s and four x s (or, perhaps, four y s and three t s). If y is associated with the qualitative factor univalent cation , then y would be the average block difference in response between the experiments involving Li and the overall mean y and y, would be the corresponding differences for experiments involving Na and K. Similarly, x g, Xj-, x, and Xgj would be the average treatment differences for experiments involving the divalent cations Mg, Ca, Sr, and Ba. Thus, the full model would be... 

This group of membranes is also frequently called membranes with immobile ion-exchange sites. First systems in which a diffusion potential is formedin the membrane will be considered [10, 12, 18, 19, 25, 41, 54, 70]. It will be assumed that all sites are equivalent and that each has a single negative charge, while the membrane is permeable only for cations. It will be assumed also that two types of univalent cations are present in solution 1, J and K ... 

Sometimes the activities are replaced by braces, e.g., Uml = ML -, here we prefer the former formality. The estimation of y, values by equations such as Eqs. (2.38) and (2.43) is unreliable for ionic strengths above about 0.5 M for univalent cations and anions and at even lower ionic strengths for polyvalent species. Consequently, values of (3° are rarely calculated, except for very exact purposes (see Chapter 6). Instead, measurements of equilibrium concentrations of the species involved in the reaction are used in a medium of fixed ionic strength where the ionic strength, /, is defined as I=V2l. Ci Zi M [see Eq. (2.38)]. A solution of fully ionized CaCl2 of 0.5 M concentration has an ionic strength / = H (0.5 X 2 -I- 2 X 0.5 X (-1) ) or 1.5 M. Stability constants are reported, then, as measured in solutions of 0.1 M, 0.5 M, 2.0 M, etc., ionic strength. In practice. 

Figure 5.63 A shows the relative positions of Si atoms in the a-quartz structure projected along axis z. In this simplified representation, note the hexagonal arrangement of Si atoms, which can be internally occupied by univalent cations through coupled substitution involving AF in tetrahedral position ...

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