Silver halides stabilization

It can be shown from a consideration of the overall stability constants of the ions [Ni( CN)4] 2 " (1027) and [ Ag( CN)2 ] (1021) that the equilibrium constant for the above ionic reaction is 1015, i.e. the reaction proceeds practically completely to the right. An interesting exercise is the analysis of a solid silver halide, e.g. silver chloride. 

Stabilization image dyes photography, 6,112 silver halides photography, 6, 102 Stabilizers... 

E. J. Birr, Stabilization of Photographic Silver Halide Emulsions. Focal Press, London and New York, 1974. 

Comparing the stability of the triammincs of silver halides, the chloride is more stable than the bromide, and the iodide cither does not exist or is very unstable. This is contrary to the usual observations in the ammines, where the stability of the ammine rises from chloride to iodide. In the case of the ammines of the oxy-halogen salts of silver the most unstable is the iodate, which is non-existent at ordinary pressure, then comes the bromate, and the most stable is the chlorate.3... 

Table 50 Stability Constants (log ( 2) for the Formation of the Complex Silver Halide Anions AgXj in Various Solvents...

Cationic silver halide species have been known for a long time.360 To account for the solubility of silver halides in aqueous silver(I) salts, complex ions such as Ag2X+ and AgjX2+ were proposed. Stability constants for these species (X = C1, Br- and I-) are given in Table... 

Table 51 Stability Constants (Log P) of Cationic Silver Halide Complexes Ag2X+ and Ag3X2+ in Various solvents at 24 "C380...

Hydroxyhydroquinone and pyrogallol can be used for lining reactors for vinyl chloride suspension polymerization to prevent formation of polymer deposits on the reactor walls (98). Hydroxyhydroquinone and certain of its derivatives are useful as auxiliary developers for silver halide emulsions in photographic material their action is based on the dye diffusion-transfer process. The transferred picture has good contrast and stain-free highlights (99). 5-Acylhydroxyhydroquinones are useful as stabilizer components for poly(alkylene oxide)s (100). 

In summary, there is evidence that the multitalented sulfur sensitization product can trap electrons, can trap holes to reduce recombination, can stabilize photolytic silver atoms, and can accelerate reduction sensitization. Conceivably, each of these properties could be of importance for latent image formation under at least some conditions. The silver sulfide centers are not of uniform size, they probably are not uniformly related energetically to the silver halide matrix, and they may differ in chemical consititution. 

Coordination compounds and coordination chemistry are involved in a number of these steps. Chemical sensitizing agents, antifoggants and stabilizers are discussed separately. This discussion concerns silver halide emulsion precipitation and physical ripening methods. 

A list of more common silver complexing agents includes thiosulfates, thiocyanates, sulfites, cyanides, ammonia and other amines, thiols, thiourea, thioacids, thioethers and alkali halides. Most are not practical as fixing agents because they fail to satisfy all the above criteria. Many find use as silver halide stabilizers (Section 59.2.1.8). These include thiocyanate, thiourea and other thioorganic compounds. These and other complexing agents such as cyclic imides, phosphines and arsines find use in silver halide diffusion transfer processes (Section 59.2.1.6). 

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