To silver

To comply with existing and future legislation with respect to silver content in processor rinsing water, the approach developed by Agfa is threefold. 

This is attributed to the different nature of the bonding of sulphur to silver as compared to gold and the slightly different packing density. The coherence length detennined with He atom diffraction was found to be 12 mn [162]. 

It is a colourless gas which decomposes on heating above 420 K to give metallic tin, often deposited as a mirror, and hydrogen. It is a reducing agent and will reduce silver ions to silver and mercury(II) ions to mercury. SnSn bonding is unknown in hydrides but does exist in alkyl and aryl compounds, for example (CH3)3Sn-Sn(CH3)3. 

The insoluble halides can be prepared by adding the respective halide ion to silver ions ... 

All the silver halides are sensitive to light, decomposing eventually to silver. In sunlight, silver chloride turns first violet and finally black. The use of these compounds in photography depends on this (see below). (All silver salts are, in fact, photosensitive—the neck of a silver nitrate bottle is black owing to a deposit of silver.)... 

In ammoniacal solution (in which the ion [AgfNHjlj]" is formed) it is readily reduced to silver (see above) by many organic compounds. The use of silver nitrate for marking clothes depends on its reduction by the material to black silver. The reduction also occurs even when the neutral solution comes in contact with the skin, and a black stain is left. Thus solid silver nitrate rubbed on the skin leaves a black deposit and so is used in surgery as a mild caustic—hence the old name for silver nitrate of lunar caustic. 

Copper is reddish and takes on a bright metallic luster. It is malleable, ductile, and a good conductor of heat and electricity (second only to silver in electrical conductivity). 

The silver ion in silver chloride can be readily reduced by light, and is used to a great extent in photographic print papers. Sufficient light intensity and time leads to silver chloride decomposing completely into silver and chlorine. 

Silver Fluoride. Silver fluoride, AgF, is prepared by treating a basic silver salt such as silver oxide or silver carbonate, with hydrogen fluoride. Silver fluoride can exist as the anhydrous salt, a dihydrate [72214-21-2] (<42° C), and a tetrahydrate [22424-42-6] (<18° C). The anhydrous salt is colorless, but the dihydrate and tetrahydrate are yellow. Ultraviolet light or electrolysis decomposes silver fluoride to silver subfluoride [1302-01 -8] Ag2p, and fluorine. 

In the absence of organic matter, silver nitrate is not photosensitive. It is easily reduced to silver metal by glucose, tartaric acid, formaldehyde, hydrazine, and sodium borohydride. 

Silver sulfate decomposes above 1085°C into silver, sulfur dioxide, and oxygen. This property is utilized ia the separation of silver from sulfide ores by direct oxidation. Silver sulfate is reduced to silver metal by hydrogen, carbon, carbon monoxide, zinc, and copper. 

In secondary wastewater treatment plants receiving silver thiosulfate complexes, microorganisms convert this complex predominately to silver sulfide and some metallic silver (see Wastes, INDUSTRIAL). These silver species are substantially removed from the treatment plant effluent at the settling step (47,48). Any silver entering municipal secondary treatment plants tends to bind quickly to sulfide ions present in the system and precipitate into the treatment plant sludge (49). Thus, silver discharged to secondary wastewater treatment plants or into natural waters is not present as the free silver ion but rather as a complexed or insoluble species. 

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. 

There are several requirements for a good sensitizing dye. A good dye is adsorbed strongly to silver haUde. The dye molecules attach themselves to the surface of the silver haUde crystals, usually up to monolayer coverage. This amount can be deterrnined by measuring the adsorption isotherm for the... 

---