Silver ions, oxidation

A silver ions oxidized at the anode and depositing on the fork, which acts as the cathode... 

Aldehydes are oxidized not only by the same reagents that oxidize primary and secondary alcohols—permanganate and dichromate—but also by the very mild oxidizing agent silver ion. Oxidation by silver ion requires an alkaline medium to prevent precipitation of the insoluble silver oxide, a complexing agent is added ammonia... 

The dehydration-reduction of Ag+ ions in the zeolite pores to form silver clusters may involve two steps. The first occurs at a temperature lower than 250 °C, and, in this process, the silver ions oxidize the water molecules and are themselves reduced the second step in the process is a nonaqueous reaction, involving the oxidation of framework oxygen ions, and the reaction Equation (9.4) is as follows ... 

Silver ions oxidize ferrous ions according to the equation ... 

Looking at our example above, we could describe the process by saying that silver ions oxidize copper metal. Or we could say that copper metal reduces silver ions. Neither of these statements is any more or less correct than the other because both processes must occur together. The same idea can be generalized to give the following terminology ... 

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. 

Silver Thiosulfate. Silver thiosulfate [23149-52-2], Ag 2 y is an insoluble precipitate formed when a soluble thiosulfate reacts with an excess of silver nitrate. In order to minimize the formation of silver sulfide, the silver ion can be complexed by haUdes before the addition of the thiosulfate solution. In the presence of excess thiosulfate, the very soluble Ag2(S203) 3 and Ag2(S203) 3 complexes form. These soluble thiosulfate complexes, which are very stable, are the basis of photographic fixers. Silver thiosulfate complexes are oxidized to form silver sulfide, sulfate, and elemental sulfur (see Thiosulfates). 

Electroplating. Most silver-plating baths employ alkaline solutions of silver cyanide. The silver cyanide complexes that are obtained in a very low concentration of free silver ion in solution produce a much firmer deposit of silver during electroplating than solutions that contain higher concentrations. An excess of cyanide beyond that needed to form the Ag(CN)2 complex is employed to control the concentration. The silver is added to the solution either directly as silver cyanide or by oxidation of a silver-rod electrode. Plating baths frequently contain 40—140 g/L of silver cyanide... 

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. 

The darkening reaction involves the formation of silver metal within the silver haUde particles containing traces of cuprous haUde. With the formation of metallic silver, cuprous ions are oxidized to cupric ions (1,4). The thermal or photochemical (optical bleaching) reversion to the colorless or bleached state corresponds to the reoxidation of silver to silver ion and the reduction of cupric ion to reform cuprous ion. 

Fig. 9. Corrosion model of silver development. As the haUde ion, X, is removed into solution at the etch pit, the silver ion,, travels interstitiaHy, Ag/ to the site of the latent image where it is converted to silver metal by reaction with the color developer, Dev. Dev represents oxidized developer.

Electrochemical treatment of the polymers in nitric acid in the absence of silver ions was carried out at room temperature. Extent of oxidation was low for hd-PE and PP. It was not possible to directly compare the results with those obtained for oxidation in the presence of silver ions since different temperatures were used (room temperature versus 60°C). However, the spectra obtained after treatment indicated similar chemical effects for the two cases. For PS, it was possible to make direct comparisons because the same temperature was used for treatment in the presence and absence of silver ions. In that case, the overall degree of oxidation was lower. 

A slight excess of a 10% sodium hydroxide solution was added to a solution of 23 grams of silver nitrate in 300 cc of water. The precipitated silver oxide was washed free of silver ion with distilled water. To a suspension of the silver oxide in 200 cc of water, a solution of 25 grams of (3-hydroxyphenyl)ethyl dimethylammonium iodide in 300 cc of water was added. The precipitate of silver iodide was removed by filtration and the filtrate concentrated to a volume of about 100 cc In vacuo. The remainder of the water was removed by lyophilization. (3-hydroxyphenyl)ethyl dimethylammonium hydroxide was obtained as a hygroscopic, amorphous solid,... 

Copper metal can reduce silver ions to metallic silver The copper is oxidized to copper ions according to the reaction... 

Thus, Experiment 7 involved the same oxidation-reduction reaction but the electron transfer must have occurred locally between individual copper atoms (in the metal) and individual silver ions (in the solution near the metal surface). This local transfer replaces the wire middleman in the cell, which carries electrons from one beaker (where they are released by copper) to the other (where they are accepted by silver ions). 

By the half-cell potentials, we conclude the Zn-Zn+2 half-reaction has the greater tendency to release electrons. It will tend to transfer an electron to silver ion, forcing (54) in the reverse direction. Hence we obtain the net reaction by subtracting (54) from (52). But remember that this subtraction must be in the proportion that causes no net gain or loss of electrons. If two electrons are lost per atom of zinc oxidized in (52), then we must double half-reaction (54) so that two electrons will be consumed. 

Precipitation reactions. These depend upon the combination of ions to form a simple precipitate as in the titration of silver ion with a solution of a chloride (Section 10.74). No change in oxidation state occurs. 

Less important oxides are Ag203, obtained impure by extended anodic oxidation of silver, and Ag30, obtained hydrothermally from Ag/AgO at 80°C, 4000 bar, which is a metallic conductor with the anti-BiI3 structure containing an hep array of silvers with oxide ions occupying 2/3 of the octahedral holes [32]. 

For example, consider the net ionic equation for the oxidation of copper metal to copper(II) ions by silver ions (Fig. K.6) ... 

Dichromate oxidation of secondary alcohols produces ketones in good yield, with little additional oxidation. For example, CH,CH2CH(OH)CH3 can be oxidized to CH CH2COCH3. The difference between the ease of oxidation of aldehydes and that of ketones is used to distinguish them. Aldehydes can reduce silver ions to form a silver mirror—a coating of silver on test-tube walls—with Tollens reagent, a solution of Ag1" ions in aqueous ammonia (Fig. 19.3) ... 

Peroxodisulfate ions oxidize aromatic amines md phenols to colored derivatives, paitic ularly under the catalytic influence of silver ions [1-4]. 

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