Monovalent ions silver

Silver occurs naturally in several oxidation states, the most common being elemental silver (Ag°) and the monovalent ion (Ag+). Soluble silver salts are, in general, more toxic than insoluble salts. In natural waters, the soluble monovalent species is the form of environmental concern. Sorption is the dominant process that controls silver partitioning in water and its movements in soils and sediments. As discussed later, silver enters the animal body through inhalation, ingestion, mucous membranes, and broken skin. The interspecies differences in the ability of animals to accumulate, retain, and eliminate silver are large. Almost all of the total silver intake is usually... 

The pH dependence of the rate of development by hydroxylamine indicates that the monovalent ion is the active species. The rate varies as about the 0.65 power of the hydroxylamine concentration at pH 12.7 and the 0.75 power at pH 10.8. These results suggest adsorption of the hydroxylamine ion, and are in complete agreement with previous findings for the catalyzed reduction of silver chloride precipitates. 

The spectra of silver and gold nanoclusters are intense and distinct (Table 4). They are thus particularly suitable to detect the evolution of a cluster composition during the construction of a bimetallic cluster in mixed solution. The system studied by pulse radiolysis was the radiolytic reduction of a mixed solution of two monovalent ions, the cyano-silver and the cyano-gold ions Ag(CN)2 and Au(CN)2 (Fig- 7) [66]. Actually, the time-resolved observation demonstrated a two-step process. First, the atoms Ag and Au are readily formed after the pulse and coalesce into an alloyed oligomer. However, due to... 

Class I and/or II MTs have been described in all animals examined. Mammalian MTs have been some of the most extensively studied of the 61 or 62 amino acids, 20 are cysteine residues. Metal ions are bound to the MT exclusively through thiolate bonds involving all 20 cysteines (see Hamer, 1986). They associate with a wide range of metals in vitro, 18 different metals in the case of rat liver MT (Nielson etal., 1985). Divalent and trivalent metals exhibit saturation binding at 7 mole equivalents forming M7-MT, whereas copper (Cu(I)) and silver (Ag(I)) bind as monovalent ions forming M12-MT. The structure of these molecules is such that two metal-binding domains are formed an a-cluster from the carboxy-terminal portion of the protein, contains 11 cysteines which bind either 4 divalent or 6 monovalent ions the (3-cluster, the amino-terminal... 

Silver is a rare element, which occurs naturally in its pure form as a white, ductile metal, and in ores. It has an average abundance of about 0.1 ppm in the earth s crust and about 0.3 ppm in soils. There are four oxidation states (0, 1 +, 2+, and 3+) the 0 and 1 + forms are much more common than the 2+ and 3+ forms. Silver occurs primarily as sulfides, in association with iron (pyrite), lead (galena), and tellurides, and with gold. Silver is found in surface waters in various forms (1) as the monovalent ion (e.g., sulphide, bicarbonate, or sulfate salts) (2) as part of more complex ions with chlorides and sulfates and (3) adsorbed onto particulate matter. 

Silver forms monovalent ion in solution, which is colourless. Silver(II) compounds are unstable, but play an important role in silver-catalysed oxidation-reduction processes. Silver nitrate is readily soluble in water, silver acetate, nitrite and sulphate are less soluble, while all the other silver compounds are practically insoluble. Silver complexes are however soluble. Silver halides are sensitive to light these characteristics are widely utilized in photography. 

The -Alumina-related Structures.—Originally the compound )3-alumina was taken to be a binary aluminium oxide, but early Y-ray structure determinations and associated chemical analysis showed that the formula was approximately NaAlnOi7. Since then a number of isostructural compounds have been characterized in which sodium is replaced by other monovalent ions, particularly silver, and aluminium by other trivalent ions, notably gallium and iron. In addition, a number of other phases have been prepared which are structurally closely related to )8-alumina. Four principal structures are known, which are labelled / ", and P"". These can also be prepared with other monovalent cations replacing sodium, and some seem only to be formed when a few per cent of divalent cations, particularly magnesium, are present, so that they are, in fact, quaternary phases. The structure and stoicheiometry of these compounds has been summarized recently and we will only consider here those aspects relevant to the present topic. 

The effects of inorganic salts on plasma cholinesterase (E16) are largely contradictory. Fruentova (F9) reported that divalent cations are more effective inhibitors of horse serum cholinesterase than are monovalent ions, whereas divalent ions are frequently reported to have a marked activating effect (H38, T8, VI). Lithium and sodium nitrates have been shown by in vitro studies of the reaction of human plasma cholinesterase with benzoylcholine to have identical inhibition profiles (W21), while sodium and potassium chlorides had very similar inhibitory actions on the hydrolysis of acetylcholine by human plasma (H47). Silver nitrate, copper sulfate, and mercuric chloride are powerful inhibitors of F. polycolor butyrylcholinesterase (N2). Cohen and Oosterbaum (C12) concluded that activation by cations occurring at the usual substrate concentration is highly dependent on the experimental conditions. This supposition is very relevant to the somewhat random choice of buffers and substrates in the work reported above. 

We can get an idea of the accuracy required in potentiometric measurements from the percent error caused by a 1-mV error in the reading at 25 °C. For an electrode responsive to a monovalent ion such as silver,... 

Pulse radiolytic studies of the kinetics of formation of clusters containing two different metals are more readily accessible, for the reasons given above, when both ions may be reduced by a monoelectronic process. This can be achieved with mixed solutions of the monovalent ions Ag and Au, in the form of KAg(CN)2 and KAu(CN)2. " The evolution of the optical absorption spectrum with time was followed specifically at 400 and 520 nm, which correspond to the maxima of the surface plasmon bands of the monometallic silver and gold clusters, respectively. The early steps of the mechanism are rapid reductions of Ag and Au into atoms... 

Silver occurs naturally in several oxidation states, usually as Ag and Ag" " other possible oxidation states of silver are Ag " " and Ag +. In surface freshwater, silver may be found as the monovalent ion in combination with sulfide, bicarbonate, or sulfate as part of more complex ions with chlorides and sulfates and adsorbed onto particulate matter. In the aqueous phase, silver at the lowest concentrations exists as either a simple AgSH or as a simple polymer HS-Ag-S-Ag-SH. At higher concentrations, colloidal Ag2S or polysulfide complexes are formed. Ag binds strongly with in inorganic and organic... 

The most widely used titrant for such determinations is diamino-ethane-tetra-acetic acid (ethylenediamine tetra-acetic acid) which is conveniently employed as the disodium salt, referred to throughout this book as EDTA. (The titrant is referred to in the B,P, and B,P,C, as sodium edetate, but this synonym has not gained universal acceptance.) Many other amino-polycarboxylic acids have been used and in certain special applications they may have some advantage for routine pharmaceutical work, however, it has not been found necessary to use any titrant other than EDTA. This substance reacts stoichiometrically with most metals to form a 1 1 complex and, usually, the reaction is instantaneous (but see Aluminium, p. 32). pH has a marked effect on the stability of the complexes formed the alkaline earth metals form complexes that are stable in alkaline solution but decompose in neutral and acid solution aluminium, copper, lead and mercury all complex under mildly acid conditions while bismuth and ferric iron form stable complexes in a solution as acid as pH 1. The monovalent ions of sodium, potassium and silver form complexes that are too weak to be used for titration purposes whilst mercurous mercury forms no complex,... 

Departures from the ideal behavior expressed by equation 7 usually are found in alkaline solutions containing alkaH metal ions in appreciable concentration, and often in solutions of strong acids. The supposition that the alkaline error is associated with the development of an imperfect response to alkaH metal ions is substantiated by the successhil design of cation-sensitive electrodes that are used to determine sodium, silver, and other monovalent cations (3). 

Tetrasilver tetroxide is a powerful oxidizer for sanitizing swimming pools, hot tubs, and industrial cooling system waters (see Water, treatment of SWIMMINGPOOLS, SPAS, AND HOT tubs). This oxide is slightly soluble and its dissociation into silver ions is enhanced by the addition of the oxidizer KgSgOg. Bivalent and trivalent silver disinfectants have been shown to be from 50 to 200 times more effective as sanitizers than monovalent silver compounds. 

Results with Sr ] in Mice. While the results with Ag cryp-tate were encouraging, we sought further preliminary evidence of the potential value of labeled cryptates as blood-flow radiopharmaceuticals. There were several reasons for these studies the monovalent silver ion is very polarizable and thus may not be a general model for monovalent cations (5,17). In contrast, divalent cations form stronger inclusive cryptates than monovalent cations of the same ionic radii. On the other hand, the added charge of the divalent ion would require that the cryptand shield more charge if it is to result in an equally lipophilic complex. 

In the case of AgCls, the two ions involved (Ag+ and Cl-) exhibit the same valence. A mineral solubility example is presented below where the cation is monovalent but the anion is divalent. Consider the solid silver sulfide Ag2Ss,... 

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