Emulsion photographic

Dispersed phase Dispersion medium Colloidal system Example 

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Various uses have been proposed for aminothiazoles in the field of photography. The more representative examples are given in Table VI-15. The 4-aminothia2ole derivative (425) has been reported to be efficient fog stabilizer for photographic emulsions (1019) (Scheme 241). 

Thiazole disulfides are reported to yield quantitatively A-4-thiazoline-2-thiones under treatment with zinc powder in acetic acid (326). The disulfide bond can be broken on heating at 100 to 260°C and (or) by alkali. This property has been used for photographic emulsions (327). The disulfide (136) (R = 4-(D-arabmo-tetrahydroxybutyD can be cleaved readily by aqueous sodium hydroxyde. carbonate, or hydrogen carbonate (149) to give 135 a by-product, 4-(D-arabino-ietrahydroxybutyl) thiazole... 

Alkyl -C(0)N(RIC1S NH- Small amounts stabilize photographic emulsion 319... 

Sensitizers as well as desensitizers form a reversal oxidoreduction system with silver halides, according to both pH and pAg of the photographic emulsion. But besides the specific influence of the emulsion, the efficiency of a sensitizing dye depends on many other factors such as its adsorption, its spectral absorption, the energetic transfer yield, the dye aggregate to the silver halide, and finally on its desensitizing property in... 

G. E. Duffin, Photographic Emulsion Chemistry, Eocal Press, London, 1966. 

Uses. Thiosalicylic acid has been used as an anthelmintic, bactericide, and fungicide. It has also been used as a mst remover, a corrosion inhibitor for steel, and a polymerization inhibitor. In photography, it has apphcation in print-out emulsions and as an activator for photographic emulsions. 

The manufacture of silver nitrate for the preparation of photographic emulsions requires silver of very high purity. At the Eastman Kodak Company, the principal U.S. producer of silver nitrate, 99.95% pure silver bars are dissolved in 67% nitric acid in three tanks coimected in parallel. Excess nitric acid is removed from the resulting solution, which contains 60—65% silver nitrate, and the solution is filtered. This solution is evaporated until its silver nitrate concentration is 84%. It is then cooled to prepare the first crop of crystals. The mother Hquor is purified by the addition of silver oxide and returned to the initial stages of the process. The cmde silver nitrate is centrifuged and recrystallized from hot, demineralized water. Equipment used in this process is made of ANSI 310 stainless steel (16). 

Sulfur Complexes. Silver compounds other than sulfide dissolve in excess thiosulfate. Stable silver complexes are also formed with thiourea. Except for the cyanide complexes, these sulfur complexes of silver are the most stable. In photography, solutions of sodium or ammonium thiosulfate fixers are used to solubilize silver hahdes present in processed photographic emulsions. When insoluble silver thiosulfate is dissolved in excess thiosulfate, various silver complexes form. At low thiosulfate concentrations, the principal silver species is Ag2(S203) 2j high thiosulfate concentrations, species such as Ag2(S203) 3 are present. Silver sulfide dissolves in alkaline sulfide solutions to form complex ions such as Ag(S 2 Ag(HS) 4. These ions are... 

Cadmium nitrate is the preferred starting material for Cd(OH)2 for use as the anode ia alkaline batteries. The siatered anode matrix of such batteries is saturated with cadmium nitrate (480—500 g/L Cd) and cadmium hydroxide is formed thereia by standardized electrolysis and dryiag (37). The tetrahydrate sells for 29.10/kg ia 20 kg lots. Other uses iaclude photographic emulsions and as a colorant ia glass and ceramics. 

Figure 8.28. Fragmentation results recorded in a photographic emulsion caused by the 70 MeV collision of a carbon and silver nucleus. From Greiner and Stocker (1985).

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