Agfa-gevaert

Agfa Gevaert Nv

Agva-gevaert N. V.

Benny Jansen

Frank P Michiels

Werner J Van De Wynckel

Johan August Loccufier

Dirk F De Ruijter

Govert De Baecke

Patrick Albert Mertens

Ton Rutges

Guy Damen

Paul Smet

An apparatus is disclosed for electrolytic desilvering of photographic processing solutions, more particularly fixing solutions or bleach-fixing solutions, comprising an electrolysis unit equiped with a monitoring system comprising a cathode, an anode and a reference electrode, characterized in that said reference electrode is a pH sensitive electrode. The desilvering is preferably performed under potentiostatic conditions. Whe using a pH sensitive reference electrode the cathodic plating potential is automatically corrected for pH changes. A preferred pH sensitive electrode is a glass electrode.

PH sensitive reference electrode in electrolytic desilvering

A black-and-white silver halide developer composition has been disclosed comprising, besides one or more developing agent(s), agent(s) preventing oxidation thereof and agent(s) providing pH buffering, at least one silver complexing agent, characterized in that said silver complexing agent has a silver complexing stability ratio of at least 70% and, besides said silver complexing agent, at least one agent preventing silver dissolution characterized in that said agent preventing silver dissolution, if present in an amount of 50 mg/l of developer, makes silver content of the developer decrease in an amount of more than 50% versus in the absence thereof, without loss in speed in an amount of more than 0.10 log Exposure after processing in said developer composition.

Developer composition for use in the processing of light-sensitive silver halide photographic materials

Processing method of light-sensitive silver halide photographic materials showing less tendency to sludge formation

A silver-containing solution is de-silvered in an electrolytic cell having an anode and a cathode. The diffusion limitation current density of the electrolytic cell is estimated by measuring a current flow there-through and silver is deposited on the cathode at a de-silvering current density which is lower than the diffusion limitation current density.

Process for de-silvering of a silver-containing solution

Silver is recovered from solutions containing the same, e.g. photographic processing solutions, in an electrolytic cell including an anode, a removable cathode and electrical connectors therefore on the exterior of the cell. The removable cathode is circular in configuration and encircles the anode. On the interior of the cell, electrical contact is made around the upper end of the cathode by means of an annular contact surface providing a large area of contact and minimizing the risk of occurrence of a corrosive connection. The upper end of the cathode is shaped for deformation, preferably in the form of castellations, and is clampingly pressed against the contact surface by a frusto-conical extension of the lid of the cell. The lid fits in threadwise engagement within the opening to the cell through which the cathode can be removed. As the lid is threaded into the cell opening, the frusto-conical extension thereof bears against the deformable cathode end portion and clamps the same against the contact surface. In this arrangement, the contact surface is situated above the level of the electrolyte in the cell so as to be protected against corrosion by the electrolyte.

Apparatus for the electrolytic recovery of silver

An electrode for use in an electrolytic cell is disclosed, comprising a generally flat sheet (50) of flexible material having at least one electrically conductive surface. Upper and lower securing means are provided each comprising a tongue (55a,b) formed on one side edge (53) of the sheet (50) and a slot (56a,b) associated with an opposite side edge (54) of the sheet (50). The tongues and slots co-operate to enable the sheet (50) to be folded into and secured in an open frusto-conical configuration. This arrangement gives ease of removal from an electrolytic cell after use and advantages of requiring less storage and transport space in a flat configuration.

Growing community of inventors

Geel, Belgium

Benny Jansen