Other Univalent Metal Ions

Other Univalent Metal Ions.—The reductions of cobalt(iri) complexes by univalent zinc, cadmium, and nickel ions have been studied in aqueous solutions, using pulse radiolysis techniques. Radiolysis of aqueous solutions of bivalent metal salts and cobalt(m) complexes involve reactions of the type (5)—(7). When the cobaltic complex concentrations are 

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Chemical Properties. In addition to the reactions Hsted in Table 3, boron trifluoride reacts with alkali or alkaline-earth metal oxides, as well as other inorganic alkaline materials, at 450°C to yield the trimer trifluoroboroxine [13703-95-2] (BOF), MBF, and MF (29) where M is a univalent metal ion. The trimer is stable below — 135°C but disproportionates to B2O2 and BF at higher temperatures (30). 

Unlike boron, aluminum, gallium, and indium, thallium exists in both stable univalent (thaHous) and trivalent (thaUic) forms. There are numerous thaHous compounds, which are usually more stable than the corresponding thaUic compounds. The thaUium(I) ion resembles the alkaU metal ions and the silver ion in properties. In this respect, it forms a soluble, strongly basic hydroxide and a soluble carbonate, oxide, and cyanide like the alkaU metal ions. However, like the silver ion, it forms a very soluble fluoride, but the other haUdes are insoluble. Thallium (ITT) ion resembles aluminum, gallium, and indium ions in properties. 

Ion solvation has been studied extensively by potentiometry [28, 31]. Among the potentiometric indicator electrodes used as sensors for ion solvation are metal and metal amalgam electrodes for the relevant metal ions, pH glass electrodes and pH-ISFETs for H+ (see Fig. 6.8), univalent cation-sensitive glass electrodes for alkali metal ions, a CuS solid-membrane electrode for Cu2+, an LaF3-based fluoride electrode for l , and some other ISEs. So far, method (2) has been employed most often. The advantage of potentiometry is that the number and the variety of target ions increase by the use of ISEs. 

A titration based on complex formation is called a complexometric titration. Ligands other than NTA in Figure 12-4 form strong 1 1 complexes with all metal ions except univalent ions such as Li, Na+, and K+. The stoichiometry is 1 1 regardless of the charge on the ion. 

Paramagnetic species formed by reactions of the radiation-produced transient species in ice and frozen aqueous systems have been studied by ESR technique. The radiation-produced electrons have been found to react e.g. with acidic solutes to form H-atoms and with group 11(b) metal ions to give the corresponding univalent radical ions, while the holes can react with anions such as S04 2 and H2P04 giving the radical ions S04 and HP04. Evidence that the electron and hole are coupled to each other, and may in fact exist in irradiated pure ice primarily in an (exciton-like) bound state has been discussed. The present work provides evidence for the reactions of the radiation-produced positive holes apart from the reactions of the electrons. 

Lithium Ion.—The colourless univalent lithium ion, Li, is characterized by the formation of salts of slight solubility with the anions of carbonic, hydrofluoric, and phosphoric acid, a distinction from the ions of the other alkali-metals, and an indication of the smaller electro-affinity of the lithium ion.12 The comparatively low electroaffinity corresponds with that of strontium, and is associated with the power of the lithium salts to form complexes with ammonia in aqueous solution, and with water to yield various crystalline hydrates. In solution in... 

Caesium Ion.—Caesium forms colourless univalent ions. It is the most electropositive of the elements, its great electroaffinity corresponding with the ready solubility of its salts. The salts with strong anions are less soluble than the corresponding derivatives of the other alkali-metals.11... 

Although other sources of entropy change are to be found in AS°, these would remain relatively constant for various metal ions compared to ASjj2q. This relationship is shown in Figure 3 for normal and expanded forms of 1200 EW Nafion using both univalent and divalent ion selectivity coefficients. Lines are least squares fits for alkali metal ions and alkaline earth ions. 

Table 18 lists values of AGp for the partitioning of the alkali metal ions, including hydrogen ion and several other univalent ions, between water and several water-immiscible organic solvents. Some of the values listed were in fact originally determined from salt-partitioning or cation-exchange data. Other values were determined from electrochemical and potentiometric experiments. 

The elements Li-Cs are aU similar but also show important differences. Their electron shells have a single s-electron in the outermost orbit, and they all form univalent ions in water solution. With water the metals react vigorously - almost explosively -with formation of hydroxides. Being the smallest of the alkali metal atoms, lithium has its Is-electron near the core and so has the highest ionization energy. In fact it is less reactive than the other alkali metals and more like magnesium. The big cesium atom on the other hand is easiest to ionize (oxidize) and is, as a consequence, the most reactive of all metals. 

The kinetics of autoxidation of L-ascorbic acid catalysed by Cu+ ions have been determined. Important features of the autoxidation, including the formation of hydrogen peroxide as a stable intermediate and of a ternary complex containing oxygen, copper(i), and ascorbate, were discussed. Reagents that complexed Cu+ ions were shown to inhibit the autoxidation. Cu+ apparently remains formally univalent throughout the entire reaction cycle and acts as an electron carrier between two substrate molecules. Other workers have shown that the metal-ion-catalysed oxidation of L-ascorbic acid at alkaline pH values is inhibited by superoxide dismutase. The kinetics and mechanism of the oxida-... 

Divalent cations, univalent cations, or both are essential cofactors for a large number of enzymes. Kinases as a class, for example, share the requirement for such cations, while in other instances, other metal ions are inhibitors of metal-activated enzymes, e.g., activation by Mg " and inhibition by Ca for many kinases and synthetases. Mildvan (1970) has reviewed the models that have been proposed to account for activation (or inhibition) of enzymes by metal ions. The "substrate bridge" and "metal bridge" models conceive of the metal ions either combining with the substrate to form a chelate or interacting with the enzyme to complete the required binding site. These complexes usually involve the active site, but Schramm (1974) has demonstrated activation of AMP nucleosidase by MgATP at a modifier site instead. 

The two water desalination applications described above represent the majority of the market for electrodialysis separation systems. A small application exists in softening water, and recently a market has grown in the food industry to desalt whey and to remove tannic acid from wine and citric acid from fruit juice. A number of other applications exist in wastewater treatment, particularly regeneration of waste acids used in metal pickling operations and removal of heavy metals from electroplating rinse waters [11]. These applications rely on the ability of electrodialysis membranes to separate electrolytes from nonelectrolytes and to separate multivalent from univalent ions. 

A similar consideration can be applied to the cathodic processes. In a solution of mercuric nitrate bivalent mercury will bo reduced to univalent until the ratio of the respective activity of the mercurous salt formed and tho mercuric salt still remaining reaches the equilibrium value. During the course of further reaction the ratio of activities of both ions in the solution will not change any longer, and metallic mercury will be deposited. Therefrom, it is evident that mercuric nitrate cannot be quantitatively reduced to mercurous salt. Bivalent mercury can be reduced practically completely to univalent in the case of mercuric chloride. As the solubility of the mercurous chloride formed by the reduction and consequently also the concentration of Hg2+ ion is very small the equilibrium between the ions in the solution will be attained only then, when nearly all Hg++ ions will be reduced to univalent ones. On the other hand on reduction of the very slightly dissociated cyanide complex Hg(CN) the equilibrium between mercurous and mercuric ions is reached at the very beginning of electrolysis as soon as a hardly noticeable amount of Hg++ ions has been formed from that moment on metallic mercury will be deposited at the cathode with practically 100 p. o. yield. 

There are few reported examples of an oxidation state other than III or V. The only simple ionic one concerns univalent bismuth, obtained by dissolving the metal in a solution of BiCl3 in HC1. There is evidence that Bi+ ions are present2 but little else is known. 

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