Palladiotype process

Other iron-based photographic systems have been devised. For example, the complex (119) can be coated with a suitable binder. Exposure reduces Fe to Fe. Treating the coating with water produces intensely colored Fe bipy complexes in exposed areas and washes unreacted salt out of unexposed areas.A system in which a ferrioxaiate complex is photolyzed to form Fe, which is then selectively complexed with a dye indicator, was discussed in Section 59.4.2. An obsolete palladiotype process relied on the photolysis of ferrioxaiate complexes to produce Fe, which in turn reduced a Pd salt to produce an image in Pd . More economical and sensitive processes today are based on amplifying a weak image in Fe or palladium nuclei by physical development. 

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