Photographic Metallized Dyes

The foregoing discussion has concerned dyes in which the metal is already present before the photographic process is initiated. However, an alternative way of making use of the superior light stability of metallized dyes consists in metallization after the photographic process. Dye developers... 

Acetonitrile also is used as a catalyst and as an ingredient in transition-metal complex catalysts (35,36). There are many uses for it in the photographic industry and for the extraction and refining of copper and by-product ammonium sulfate (37—39). It also is used for dyeing textiles and in coating compositions (40,41). It is an effective stabilizer for chlorinated solvents, particularly in the presence of aluminum, and it has some appflcation in... 

Tetrasodium hexakiscyanoferrate decahydrate [14434-22-1], Na4[Fe(CN)g] IOH2O, or yellow pmssiate of soda, forms yellow monoclinic crystals that are soluble in water but insoluble in alcohol. It is slightly efflorescent at room temperature, but the anhydrous material, tetrasodium hexakiscyanoferrate [13601 -19-9], Na4[Fe(CN)J, is obtained at 100°C. The decahydrate is produced from calcium cyanide, iron(II) sulfate, and sodium carbonate in a process similar to that for the production of K4[Fe(CN)g] 3H2O. It is used in the manufacture of trisodium hexakiscyanoferrate, black and blue dyes, as a metal surface coating, and in photographic processing. 

The Knorr pyrazole synthesis has been extensively utilized in the preparation of a number of pyrazoles as metal chelators, photographic dyes, herbicides, and biologically active... 

Iodine is used in many dyes and as a colorant for foods and cosmetics. Its silver salt is used in photographic negative emulsions. Other industrial applications include dehydrogenation of butane and butylenes to 1,3-butadiene as a catalyst in many organic reactions in treatment of naphtha to yield high octane motor fuel and in preparation of many metals in high purity grade, such as titanium, zirconium and hafnium. 

In the black and white photographic process, the dark areas result from the presence of reduced metallic silver, Ag. In the colour process metallic Ag is used to synthesize a dye of the appropriate colour, and all the silver is removed from the film. The photochemical reaction is therefore the same as in the black and white process, namely photoinduced electron transfer within the AgBr grains. 

Instant photography (e.g. of the Polaroid type) also relies indirectly on the silver halide process but here the reduced Ag (metallic silver) acts as a reducing agent to modify the solubility properties of a dye. The dye is linked covalently to a molecule such as a quinone (Figure 6.5), which is insoluble in water. When this is reduced to hydroquinone, it becomes soluble in alkaline solutions. The principle of this photographic process is the following ... 

The silver dye-bleach process depends on destruction of a dye in a photographic layer in an amount proportional to the quantity of image silver present.94 95 The dye is normally an azo dye in which the azo bond is cleaved. Over the years a variety of metal-complexed azo dyes have been described for use in this process. These dyes must be immobile they must not wander from layer to layer, or color contamination of the final image will result. However, they must be reactive enough in an aqueous environment for the azo bond to break. 

Formazan dyes have become important reactive dyes for cotton. Formazan dyes are also used in analytical chemistry because of the high color intensity of many of their metal complexes. The chemistry of formazans was first exploited in 1962 by MacDonald to produce color photographs [81],... 

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