Ciba-geigy Ag

Ekkehard Kramp

John Lenoir

Max Marthaler

Andreas Engel

Ute Eggert

Robert Schaller

This invention relates to layers for photographic materials, which comprises a polysaccharide which is formed extracellularly by bacterial fermentation of glucose, maltose, sucrose or xylose, if appropriate in the presence of yeast, yeast hydrolysate or casein-hydrolysate, and with mono-, di- and/or tri-valent metal ions, forms gels having a solidification temperature between 24.degree. and 25.degree. C. Gellan gum has proved to be a particularly advantageous polysaccharide for use in the layers according to the invention.

Layers for photographic materials

A process is described for the prevention of darkening and the formation of a sediment in photographic developer solutions which contain a silver halide developer, a water-soluble silver halide solvent and organic sulfur compounds. The organic sulfur compounds are a combination of (a) an organic thiol compound or thione compound capable of tautomerism and (b) a Bunte salt which contains groups conferring solubility in water. Developer solutions which contain the indicated combination of sulfur compounds are outstandingly stable.

Process for the prevention of darkening and the formation of a sediment

The invention relates to a dye bleach preparation which contains in addition to an acid, a water-soluble iodide and optionally a dye bleach catalyst at least one bifunctional sulphur compound having a sufficient solubility in the preparation and a low vapor pressure and containing at least one HS-group and at least one oxygen, nitrogen, phosphorus or additional sulphur atom, the sulphur atom of each HS-group being separated from the next oxygen, sulphur, nitrogen and phosphorus atom present in the molecule by at least three carbon atoms.

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Marly, Switzerland

Ekkehard Kramp