Silver halogenides

Natural silver halogenides, which are secondary ores for silver production, are characterized by intensive luminescence under powerful laser excitation (Fig. 4.67). The main source of the backgroimd liuninescence is the sorption of organic matter. The relatively long decay time of their liuninescence may enable us to lower the short-lived background emission by several orders of magnitude. 

Species that interact with potential-determining ions and alter their activity must also influence the surface potential they have been called potential-determining species of the second kind (14). For example, NH3 alters the activity of Ag and thus affects the surface potential of silver halogenides. Similarly, metal ions that coordinate with surface OH groups... 

Nowadays, the availabihty of fiber-optic probes offers several possibilities for performing in situ catalyst characterization. As quartz glass is transparent to Raman laser and UV-vis radiation, these spectroscopies are particularly versatile. Thus, the respective UV-vis probe or Raman laser optics can be focused from outside or directly immersed in the reaction solution (in the latter case, a Raman probe is used). In contrast, infrared radiation is strongly adsorbed by quartz hence, special infrared transmissive fibers are required. Such silver halogenide fibers have proven suitable and are now well established [35-37] despite their fiagihty and degradation over time. 

Two ATR-FTIR probes (Metder Toledo DiComp immersion probe connected via a flexible silver halogenide fiber to a ReactIR 45 m spectrometer) can be inserted into the reaction cell via Swagelok connections. One of these ports can also be used for sampling and separate analysis of the reaction mixture. The stainless steel container can be heated to 250 °C, with heat transferred via the polyetheretherketone (PEEK) insert to the liquid. X-rays can enter and exit the reaction mixture through a... 

The detailed chemistry and function of photographic couplers is beyond the scope of this text. It is reviewed in the literature [47]. Triazole compounds are used as photographic couplers [48]. The precipitation of silver halogenides can be performed in the presence of triazole containing polymers [49]. 

The undeveloped grains of silver halogenide are next removed, by treatment with a fixing bath, which contains thiosulfate ion, S2O3 (from sodium thiosulfate, hypo, Na2S203 5H20). The soluble silver thiosulfate complex is formed ... 

Just like other silver salts, SF darkens when exposed to light. It is practically insoluble in cold water and can therefore be re-crystaUized from hot water with high yields [35]. The solubility of silver fulminate in water at various temperatures is given in Table 3.3 [28, 29]. Solubility of SF in water is considerably higher than silver halogenides. 

Oxidative Additions. Many covalent compounds (XY) such as hydrogen, halogens, mercury and silver halogenides can react with clusters resulting in an homolytic cleavage of the X-Y bond and in the oxidative addition of the two fragments to a metal-metal bond thus increasing the formal oxidation state of the metal atoms. 

A few drops of ammonia (1 1) are introduced into the decomposition tube after the extraction with water and the solution is expelled into a micro test tube. On acidification with HNO3, a turbidity or a precipitate due to silver halogenides is formed. 

J. Nedoma, Chem. Listy., 66, 772 (1972). Solubility products of silver halogenides in fso-propanol and iso-propanol water mixtures. 

---