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EP0035008A2 - Process and apparatus for treating photographic baths - Google Patents

Process and apparatus for treating photographic baths Download PDF

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Publication number
EP0035008A2
EP0035008A2 EP81870013A EP81870013A EP0035008A2 EP 0035008 A2 EP0035008 A2 EP 0035008A2 EP 81870013 A EP81870013 A EP 81870013A EP 81870013 A EP81870013 A EP 81870013A EP 0035008 A2 EP0035008 A2 EP 0035008A2
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EP
European Patent Office
Prior art keywords
control electrode
cathode
potential
electrolysis
silver
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP81870013A
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German (de)
French (fr)
Other versions
EP0035008B1 (en
EP0035008A3 (en
Inventor
Pierre F. Vandenput
Philippe A. De Meester
Jean-Pierre J. Heraly
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Esterol AG
Original Assignee
Esterol AG
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Priority to AT81870013T priority Critical patent/ATE11602T1/en
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
    • C25C1/20—Electrolytic production, recovery or refining of metals by electrolysis of solutions of noble metals
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
    • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
    • C25C7/06—Operating or servicing
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D21/00—Processes for servicing or operating cells for electrolytic coating
    • C25D21/12—Process control or regulation
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03C—PHOTOSENSITIVE MATERIALS FOR PHOTOGRAPHIC PURPOSES; PHOTOGRAPHIC PROCESSES, e.g. CINE, X-RAY, COLOUR, STEREO-PHOTOGRAPHIC PROCESSES; AUXILIARY PROCESSES IN PHOTOGRAPHY
    • G03C5/00—Photographic processes or agents therefor; Regeneration of such processing agents
    • G03C5/26—Processes using silver-salt-containing photosensitive materials or agents therefor
    • G03C5/395—Regeneration of photographic processing agents other than developers; Replenishers therefor
    • G03C5/3954—Electrical methods, e.g. electroytic silver recovery, electrodialysis
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03D—APPARATUS FOR PROCESSING EXPOSED PHOTOGRAPHIC MATERIALS; ACCESSORIES THEREFOR
    • G03D3/00—Liquid processing apparatus involving immersion; Washing apparatus involving immersion
    • G03D3/02—Details of liquid circulation
    • G03D3/06—Liquid supply; Liquid circulation outside tanks
    • G03D3/065—Liquid supply; Liquid circulation outside tanks replenishment or recovery apparatus

Definitions

  • the present invention relates to a method and an apparatus for the treatment of a photographic fixative bath, with a view to extracting the silver in the form of metallic silver by electrolysis in a bath comprising electrodes, it is ie at least one cathode and anodes.
  • a method and an apparatus are known in which a fixer bath is subjected to electrolysis in order to recover the silver in metallic form on at least one cathode.
  • the electric electrolysis current must have a sufficiently low intensity so that the sulfurization of the silver is avoided. Due to the fact that the electrolysis current must be low, the recovery of the silver is far from complete and it sometimes happens that more than 2 grams / liter of silver is lost in the fixing baths sent to the after their electrolysis. This obviously results in a significant loss of money economically.
  • the photographic fixer bath containing an excess of antioxidant agent is subjected to an electrolysis so as to ensure the deposition metallic silver on at least one cathode placed between two anodes in the electrolytic bath, subjected to turbulence, the pH being maintained at approximately 3.5 to 4.5 and the electrolysis current being subjected in this bath to regulation depending on its silver content, the intensity of the current being brought to decrease as the silver content of the bath decreases.
  • the electrolysed bath can be used again as a photographic fixative bath.
  • the potential difference to be applied to the electrodes during electrolysis must include at least the potential difference to overcome the ohmic resistance of the electrolysis cell, the concentration polarization due to the concentration gradients in the electrolyte and the overvoltage. inherent in the rate of reactions occurring at the electrodes.
  • the electrolysis rate is related to the electrolysis current and therefore to the potential difference applied to the electrodes. To perform electrolysis fairly quickly, while avoiding side reactions in the photographic fixative bath at low concentrations of silver, the electrolysis current is modified during the operation.
  • Apparatuses for treating baths of photographic fixatives are known in which the electric electrolysis current is adjusted during electrolysis, either as a function of the silver concentration of the bath of photographic fixer, or as a function of the resistivity of the cell. electrolysis, or again depending on the overvoltage at the cathode.
  • Known devices based on the measurement of the overvoltage at the cathode use a reference electrode connected by a bridge of silver nitrate placed in the vicinity of the cathode and make it possible to control the electrolysis up to very low silver concentrations.
  • This system implies the obligation to use a set of liquid junctions of different electrolytes, such as nitrate silver and, for example, mercury chloride, when using a calomel reference electrode.
  • the migration of different ions causes, during electrolysis, irreversible phenomena which modify the value of the overvoltage at the junctions of electrolytes.
  • the present invention aims to remedy the drawbacks described above by a method according to which the intensity of the electrolysis current is adjusted by measuring both the resistivity of the electrolysis cell and the overvoltage at the electrodes by the potential difference. between a control electrode immersed in the electrolytic bath and a cathode serving as a working electrode.
  • the electrolysis current is advantageously adjusted as a function of the potential difference between a control electrode, composed of pure carbon and immersed in the electrolytic bath, and a cathode serving as a working electrode, the voltage of the control electrode being maintained at a constant reference value.
  • the apparatus for treating a photographic fixer bath according to the invention which comprises, in order to extract the silver in metallic form, as electrodes, at least one cathode and anodes, as well as an electrode control, is essentially characterized in that the control electrode is composed of pure carbon and is immersed in the stirred electrolytic bath near said or of a cathode serving as working electrode, and in that it comprises a regulating device connected to the control electrode and said cathode and arranged for adjusting the electrolysis current as a function of the potential difference between said control electrode and said cathode.
  • the device for regulating the electrolysis current comprises a connected adder assembly. tee for adding the potential of the control electrode and a predetermined reference potential; a comparator / integrator assembly having an input connected to the output of the adder assembly and a second input connected to receive the potential of said cathode, said assembly being arranged to integrate the potential difference between said control electrode and the reference potential and for comparing the integrated value to the potential of the cathode so as to produce a control signal, and a current generator connected to supply the electrolysis current in response to said control signal from the comparator / integrator assembly.
  • the method and the apparatus according to the invention aim to extract the silver contained in a photographic fixer bath as the silver bath becomes saturated, with a view to prolonging the duration of use of this bath.
  • the apparatus for treating a photographic fixer bath according to the invention shown in FIG. 1, comprises, in a known manner, an electrolysis cell 1 mounted downstream of an enclosure (not shown) in which s fixes a photographic film and the overflow of which is sent via a pipe 2 into the electrolysis cell 1.
  • the electrolysis cell 1 contains at least one cathode 3 in the form of a plate, for example made of stainless steel, disposed between two anodes 4 constituted, for example, by high density and high purity graphite. Cathode 3 and anodes 4 are held in place and guided in the cell electrolysis 1 by known means (not shown).
  • a device for stirring the electrolyte which may be constituted by a dip tube 5 whose upper end is bent as shown in 6.
  • This dip tube whose lower end is perforated to allow the entry of electrolyte in the tube, is connected a pipe 7 supplying this tube 5 with compressed air from a source of compressed air, not shown.
  • the compressed air supplied to the lower part of the dip tube 5 is expelled in mixture with liquid fixative through the free end 6, creating permanent agitation or turbulence in the intervals between the cathode 3 and the anodes 4, so that that the silver ions in the electrolytic bath are brought close to the cathode (s) 3 in order to be fixed there.
  • a control electrode 8 immersed in the electrolytic bath. This electrode which has a determined potential with respect to the cathode, plays a role which will be explained later.
  • the cathode 3, the two anodes 4 and the control electrode 8 are connected by electrical conductors to a control device mounted in a housing (not shown) in which is also mounted the compressed air supply device.
  • the photographic fixative bath used in the process according to the invention is advantageously an aqueous solution containing approximately 100 to 200 g / l of ammonium or sodium thiosulfate and from 0 to 50 g / l of ammonium thiocyanate, as well as '' an excess of sodium sulfite up to a concentration of 60 g / 1.
  • This bath also contains a known tanning agent, at a starting concentration which can reach 15 g / liter, this concentration usually being between approximately 5 and 15 g / liter.
  • the pH of the photographic fixing bath is maintained at a value of approximately 3.5 to 4.5 by adding thereto, if necessary, a small amount of an acid, such as acetic acid.
  • the electrolysis cell 1 could contain a greater number of cathodes and anodes, the number of anodes always being one unit greater than the number cathodes.
  • the electrolysis current in the electrolysis cell 1 is regulated according to the silver content of the electrolytic bath so that the current decreases when the silver content of the electrolytic bath becomes less than a predetermined low value, for example 0.5-2 g / 1.
  • This regulation is ensured from the potential of the control electrode 8 by means of a regulation device 10 illustrated diagrammatically in FIG. 2.
  • This device is organized to maintain the potential Uec of the control electrode 8 at a predetermined set value and to compare this potential with the potential of the cathode 3 in order to adjust the electrolysis current.
  • the potential Uec of the control electrode 8 is applied by line 103 to a terminal 101 of the regulating device 10.
  • To a second terminal 102 is applied the predetermined reference or reference potential Uref.
  • the potentials Uec and Uref are of opposite polarities and are added by a circuit of resistors 11: the sum of these potentials is applied to a first input 104 of an operational amplifier 12.
  • a second input 105 of this amplifier receives the potential Uc from the cathode 3 via the line 106 through the resistor 13.
  • An integration capacitor 14 is connected in parallel with the amplifier 12.
  • the current on line 104 is zero and the voltage across the terminals of capacitor 14 is at a constant value.
  • the voltage on the output line 107 of the amplifier 12 controls a current generator 15 to generate a current which, after amplification in the amplifier 16, supplies the anodes 4 to supply the electrolysis current.
  • the reference potential Uref is chosen to be equal to the potential that the control electrode 8 would take for a concentration of the electrolytic bath of the order of 0.5 to 2 g / l with a zero electrolysis current.
  • the reference potential Uref is for example from 300 to 600 millivolts.
  • the control electrode 8 is advantageously polarized by a low current, of 1 mA for example, to protect this electrode against damage which would be caused at the surface.
  • a low current of 1 mA for example.
  • the control electrode 8 is protected by a sheath 9, for example made of foam, to avoid turbulence of the electrolytic bath in the immediate vicinity of this electrode, such turbulence possibly having the effect of causing an undesirable variation in the potential of this electrode.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Silver Salt Photography Or Processing Solution Therefor (AREA)
  • Photographic Developing Apparatuses (AREA)

Abstract

The process for treating a photographic fixing bath, in order to remove therefrom the silver in metallic form by electrolysis in an electrolysis cell comprising at least one cathode on which the silver is deposited, two anodes and a control electrode placed in the vicinity of the cathode, comprises the step of adjusting the intensity of the electrolysis current by measuring the potential difference between a cathode serving as a working electrode and the control electrode. The apparatus for treating a photographic fixing bath in order to remove therefrom the silver comprises an electrolytic cell containing, as electrodes, at least one cathode and anodes as well as a control electrode made of pure carbon immersed in a stirred electrolytic bath, the voltage of this control electrode being maintained at a constant reference value and the potential on this control electrode serving to control the electrolysis current in operation.

Description

La présente invention est relative à un procédé et à un appareil pour le traitement d'un bain de fixateur photographique, en vue d'en extraire l'argent sous forme d'argent métallique par électrolyse dans un bain comportant des électrodes, c'est-à-dire au moins une cathode et des anodes.The present invention relates to a method and an apparatus for the treatment of a photographic fixative bath, with a view to extracting the silver in the form of metallic silver by electrolysis in a bath comprising electrodes, it is ie at least one cathode and anodes.

On connait un procédé et un appareil dans lesquels on soumet un bain de fixateur à une électrolyse en vue de récupérer l'argent sous forme métallique sur au moins une cathode. Dans ce procédé et cet appareil connus, le courant électrique d'électrolyse doit présenter une intensité suffisamment faible pour que l'on évite la sulfuration de l'argent. En raison du fait que le courant d'électrolyse doit être faible, la récupération de l'argent est loin d'être complète et il arrive parfois que plus de 2 grammes/litre d'argent soient perdus dans les bains de fixage envoyés à l'égoût après leur électrolyse. Ceci se traduit évidemment par une perte d'argent importante sur le plan économique.A method and an apparatus are known in which a fixer bath is subjected to electrolysis in order to recover the silver in metallic form on at least one cathode. In this known process and this apparatus, the electric electrolysis current must have a sufficiently low intensity so that the sulfurization of the silver is avoided. Due to the fact that the electrolysis current must be low, the recovery of the silver is far from complete and it sometimes happens that more than 2 grams / liter of silver is lost in the fixing baths sent to the after their electrolysis. This obviously results in a significant loss of money economically.

De plus, les législations des pays industrialisés ne tolèrent plus l'évacuation à l'égoût de bains de fixateurs photographiques contenant des sels d'argent. Bien que les législations diffèrent d'un pays à l'autre, on peut affirmer que la quantité maximale que peuvent contenir les bains de fixateurs photographiques est de l'ordre de 0,1 mg d'argent par litre d'eaux usées. En pratique, on se trouve donc dans l'obligation de n'envoyer à l'égoùt que des bains sensiblement exempts d'argent, la mesure de la teneur en argent de ces bains devant s'effectuer à la sortie de l'appareil de développement photographique.In addition, the laws of industrialized countries no longer allow the evacuation of photographic fixatives containing silver salts into the drain. Although the laws differ from one country to another, it can be said that the maximum quantity that can hold photographic fixative baths is around 0.1 mg of silver per liter of wastewater. In practice, therefore, we are obliged to send only substantially silver-free baths to the sewer, the measurement of the silver content of these baths being carried out at the output of the camera.

Dans un procédé connu de traitement d'un bain de fixateur photographique en vue d'en extraire l'argent sous forme métallique, on soumet le bain de fixateur photographique contenant un excès d'un agent antioxydant à une électrolyse de manière à assurer le dépôt d'argent métallique sur au moins une cathode disposée entre deux anodes dans le bain électrolytique, soumis à une turbulence, le pH étant maintenu à environ 3,5 à 4,5 et le courant d'électrolyse étant soumis dans ce bain à une régulation en fonction de sa teneur en argent, l'intensité du courant étant amenée à diminuer à mesure que la teneur en argent du bain décroit. Le bain électrolysé peut être utilisé à nouveau comme bain de fixateur photographique.In a known method of treating a photographic fixer bath with a view to extracting the silver in metallic form, the photographic fixer bath containing an excess of antioxidant agent is subjected to an electrolysis so as to ensure the deposition metallic silver on at least one cathode placed between two anodes in the electrolytic bath, subjected to turbulence, the pH being maintained at approximately 3.5 to 4.5 and the electrolysis current being subjected in this bath to regulation depending on its silver content, the intensity of the current being brought to decrease as the silver content of the bath decreases. The electrolysed bath can be used again as a photographic fixative bath.

La différence de potentiel à appliquer aux électrodes au cours de l'électrolyse doit comprendre au moins la différence de potentiel pour vaincre la résistance ohmique de la cellule d'électrolyse, la polarisation de concentration due aux gradients de concentration dans l'électrolyte et la surtension inhérente à la vitesse des réactions se produisant aux électrodes.The potential difference to be applied to the electrodes during electrolysis must include at least the potential difference to overcome the ohmic resistance of the electrolysis cell, the concentration polarization due to the concentration gradients in the electrolyte and the overvoltage. inherent in the rate of reactions occurring at the electrodes.

Si on applique une différence de potentiel trop élevée aux électrodes lors de l'électrolyse, il se produit à l'endroit des électrodes des réactions secondaires qui nuisent à la pureté et à la qualité du dépôt d'argent sur la cathode. Il peut éventuellement se former un précipité indésirable de sulfure d'argent dans le bain de fixateur photographique.If a too high potential difference is applied to the electrodes during electrolysis, side reactions occur at the electrodes which affect the purity and the quality of the deposit of silver on the cathode. An undesirable precipitate of silver sulfide may possibly form in the photographic fixer bath.

La vitesse d'électrolyse est liée au courant d'électrolyse et par conséquent à la différence de potentiel appliquée aux électrodes. Pour effectuer l'électrolyse assez rapidement, tout en évitant des réactions secondaires dans le bain de fixateur photographique à de faibles concentrations d'argent, on modifie le courant d'électrolyse au cours de l'operation.The electrolysis rate is related to the electrolysis current and therefore to the potential difference applied to the electrodes. To perform electrolysis fairly quickly, while avoiding side reactions in the photographic fixative bath at low concentrations of silver, the electrolysis current is modified during the operation.

On connait des appareils de traitement de bains de fixateursphotographiques dans lesquels le courant électrique d'électrolyse est réglé au cours de l'électrolyse,soit en fonction de la concentration en argent du bain de fixateur photographique, soit en fonction de la résistivité de la cellule d'électrolyse, soit encore en fonction de la surtension à la cathode. Ces appareils connus ont les inconvénients suivants.Apparatuses for treating baths of photographic fixatives are known in which the electric electrolysis current is adjusted during electrolysis, either as a function of the silver concentration of the bath of photographic fixer, or as a function of the resistivity of the cell. electrolysis, or again depending on the overvoltage at the cathode. These known devices have the following drawbacks.

Les appareils connus basés sur la mesure de la concentration en argent sont coûteux et complexes.Known devices based on the measurement of the silver concentration are expensive and complex.

Les appareils connus basés sur la mesure de la variation de la résistivité du bain au cours de l'électrolyse ne donnent qu'une mesure relative de l'épuisement du bain. La résistivité de la cellule d'électrolyse varie avec la composition du bain. Il est donc nécessaire de régler l'appareil avant chaque traitement en fonction de la quantité exacte d'antioxydant et autres produits ajoutés au bain de fixateur photographique. De plus, il est indispensable de maintenir le bain à une température constante, d'où la nécessité d'un thermostat.Known devices based on the measurement of the variation of the resistivity of the bath during electrolysis give only a relative measurement of the exhaustion of the bath. The resistivity of the electrolysis cell varies with the composition of the bath. It is therefore necessary to adjust the device before each treatment according to the exact amount of antioxidant and other products added to the photographic fixative bath. In addition, it is essential to maintain the bath at a constant temperature, hence the need for a thermostat.

Les appareils connus basés sur la mesure de la surtension à la cathode utilisent une électrode de référence reliée par un pont de nitrate d'argent placé au voisinage de la cathode et permettent de contrôler l'électrolyse jusqu'à des concentrations en argent très faibles. Ce système implique cependant l'obligation d'utiliser un ensemble de jonctions liquides d'électrolytes différents, tels que nitrate d'argent et par exemple du chlorure de mercure, lorsqu'on fait usage d'une électrode de référence au calomel. La migration d'ions différents provoque, lors de l'électrolyse, des phénomènes irréversibles qui modifient la valeur de la surtension aux jonctions d'électrolytes.Known devices based on the measurement of the overvoltage at the cathode use a reference electrode connected by a bridge of silver nitrate placed in the vicinity of the cathode and make it possible to control the electrolysis up to very low silver concentrations. This system however implies the obligation to use a set of liquid junctions of different electrolytes, such as nitrate silver and, for example, mercury chloride, when using a calomel reference electrode. The migration of different ions causes, during electrolysis, irreversible phenomena which modify the value of the overvoltage at the junctions of electrolytes.

La présente invention vise à remédier aux inconvénients décrits ci-dessus par un procédé selon lequel on règle l'intensité du courant d'électrolyse en mesurant à la fois la résistivité de la cellule d'électrolyse et la surtension aux électrodes par la différence de potentiel entre une électrode de contrôle plongée dans le bain électrolytique et une cathode servant d'électrode de travail.The present invention aims to remedy the drawbacks described above by a method according to which the intensity of the electrolysis current is adjusted by measuring both the resistivity of the electrolysis cell and the overvoltage at the electrodes by the potential difference. between a control electrode immersed in the electrolytic bath and a cathode serving as a working electrode.

Suivant une particularité de l'invention, on règle avantageusement le courant d'électrolyse en fonction de la différence de potentiel entre une électrode de contrôle, composée de carbone pur et plongée dans le bain électrolytique,et une cathode servant d'électrode de travail, la tension de l'électrode de contrôle étant maintenue à une valeur de référence constante.According to a feature of the invention, the electrolysis current is advantageously adjusted as a function of the potential difference between a control electrode, composed of pure carbon and immersed in the electrolytic bath, and a cathode serving as a working electrode, the voltage of the control electrode being maintained at a constant reference value.

L'appareil de traitement d'un bain de fixateur photographique suivant l'invention, qui comporte, en vue d'en extraire l'argent sous forme métallique , comme électrodes, au moins une cathode et des anodes, ainsi qu'une électrode de contrôle, est caractérisé essentiellement en ce que l'électrode de contrôle est composée de carbone pur et est plongée dans le bain électrolytique agité à proximité de ladite ou d'une cathode servant d'électrode de travail, et en ce qu'il comprend un dispositif de régulation connecté à l'électrode de contrôle et ladite cathode et agencé pour régler le courant d'électrolyse en fonction de la différence de potentiel entre ladite électrode de contrôle et ladite cathode.The apparatus for treating a photographic fixer bath according to the invention, which comprises, in order to extract the silver in metallic form, as electrodes, at least one cathode and anodes, as well as an electrode control, is essentially characterized in that the control electrode is composed of pure carbon and is immersed in the stirred electrolytic bath near said or of a cathode serving as working electrode, and in that it comprises a regulating device connected to the control electrode and said cathode and arranged for adjusting the electrolysis current as a function of the potential difference between said control electrode and said cathode.

En particulier, le dispositif de régulation du courant d'électrolyse comprend un montage additionneur connec-. té pour additionner le potentiel de l'électrode de contrôle et un potentiel de référence prédéterminé; un montage comparateur/intégrateur ayant une entrée connectée à la sortie du montage additionneur et une seconde entrée connectée pour recevoir le potentiel de ladite cathode, ledit montage étant agencé pour intégrer la différence de potentiel entre ladite électrode de contrôle et le potentiel de référence et pour comparer la valeur intégrée au potentiel de la cathode en sorte de produire un signal de commande, et un générateur de courant connecté pour fournir le courant d'électrolyse en réponse audit signal de commande du montage comparateur/ intégrateur.In particular, the device for regulating the electrolysis current comprises a connected adder assembly. tee for adding the potential of the control electrode and a predetermined reference potential; a comparator / integrator assembly having an input connected to the output of the adder assembly and a second input connected to receive the potential of said cathode, said assembly being arranged to integrate the potential difference between said control electrode and the reference potential and for comparing the integrated value to the potential of the cathode so as to produce a control signal, and a current generator connected to supply the electrolysis current in response to said control signal from the comparator / integrator assembly.

Le procédé et l'appareil de traitement de bains de fixateurs photographiques suivant l'invention présentent les avantages suivants :

  • 1. la différence de potentiel entre l'électrode de contrôle et la cathode de travail est une mesure précise et continue à la fois de la résistivité du bain électrolytique, d'habitude assez faible,et de la surtension à la cathode de travail, ce qui n'est pas le cas dans les procédés qui font parfois intervenir deux électrodes de contrôle;
  • 2. l'absence de jonctions liquides d'électrolytes supprime les réglages de l'appareil avant chaque traitement de bain de fixateur photographique en fonction des phénomènes irréversibles qui modifient la valeur de la surtension des jonctions;
  • 3. L'appareil ne nécessite aucun réglage même si la composition des bains de fixateurs photographiques à traiter varie;
  • 4. l'appareil ne nécessite pas le maintien d'une température constante au cours de l'électrolyse.
The method and the apparatus for treating photographic fixative baths according to the invention have the following advantages:
  • 1. the potential difference between the control electrode and the working cathode is a precise and continuous measurement both of the resistivity of the electrolytic bath, usually quite low, and of the overvoltage at the working cathode, this which is not the case in the processes which sometimes involve two control electrodes;
  • 2. the absence of liquid electrolyte junctions eliminates the device settings before each photographic fixer bath treatment as a function of irreversible phenomena which modify the value of the overvoltage of the junctions;
  • 3. The device does not require any adjustment even if the composition of the photographic fixative baths to be treated varies;
  • 4. the device does not require a constant temperature to be maintained during electrolysis.

D'autres particularités et détails de l'invention ressortiront de la description qui suit dans laquelle il est fait référence aux dessins schématiques ci-annexés , dans lequels :

  • - la figure 1 est une vue en perspective avec brisures partielles d'une cellule d'électrolyse utilisée suivant l'invention;
  • - la figure 2 est une vue schématique du dispositif régulation du courant d'électrolyse suivant 1' invention.
Other particularities and details of the invention will emerge from the description which follows, in which reference is made to the attached schematic drawings, in which:
  • - Figure 1 is a perspective view with partial breaks of an electrolysis cell used according to the invention;
  • - Figure 2 is a schematic view of the device for regulating the electrolysis current according to the invention.

Dans ces différentes figures, les mêmes notations de référence désignent des éléments identiques.In these different figures, the same reference notations designate identical elements.

Le procédé et l'appareil suivant l'invention visent à extraire l'argent contenu dans un bain de fixateur photographique au fur et à mesure de la saturation de ce bain en argent, en vue de prolonger la durée d'utilisation de ce bain. L'appareil de traitement d'un bain de fixateur photographique suivant l'invention,représenté à la figure 1, comprend, de manière connue, une cellule d'électrolyse 1 montée en aval d'une enceinte (non représentée) dans laquelle s'effectue le fixage d'un film photographique et dont le trop plein est envoyé par une conduite 2 dans la cellule d'électrolyse 1.The method and the apparatus according to the invention aim to extract the silver contained in a photographic fixer bath as the silver bath becomes saturated, with a view to prolonging the duration of use of this bath. The apparatus for treating a photographic fixer bath according to the invention, shown in FIG. 1, comprises, in a known manner, an electrolysis cell 1 mounted downstream of an enclosure (not shown) in which s fixes a photographic film and the overflow of which is sent via a pipe 2 into the electrolysis cell 1.

Comme le montre la figure 1, la cellule d'électrolyse 1 suivant l'invention contient au moins une cathode 3 sous forme d'une plaque, par exemple en acier inoxydable, disposée entre deux anodes 4 constituées, par exemple, par des plaques en graphite de densité élevée et de grande pureté. La cathode 3 et les anodes 4 sont maintenues en place et guidées dans la cellule d'électrolyse 1 par des moyens connus (non montrés).As shown in FIG. 1, the electrolysis cell 1 according to the invention contains at least one cathode 3 in the form of a plate, for example made of stainless steel, disposed between two anodes 4 constituted, for example, by high density and high purity graphite. Cathode 3 and anodes 4 are held in place and guided in the cell electrolysis 1 by known means (not shown).

Dans chacun des intervalles entre la cathode 3 et les anodes 4 est prévu un dispositif d'agitation de l'électrolyte pouvant être constitué par un tube plongeant 5 dont l'extrémité supérieure est recourbée comme montré en 6. A ce tube plongeant dont l'extrémité inférieure est trouée pour permettre l'entrée d' électrolyte dans le tube, est relié un tuyau 7 alimentant ce tube 5 en air comprimé provenant d'une source d'air comprimé, non montrée. L'air comprimé amené à la partie inférieure du tube plongeant 5 est expulsé en mélange avec du fixateur liquide par l'extrémité libre 6, en créant une agitation ou turbulence permanente dans les intervalles entre la cathode 3 et les anodes 4, de telle sorte que les ions argent se trouvant dans le bain électrolytique soient amenés à proximité de la ou des cathodes 3 afin de s'y fixer. Entre la cathode 3 et une des anodes 4 est placée une électrode de contrôle 8 plongeant dans le bain électrolytique. Cette électrode qui a un potentiel déterminé par rapport à la cathode, joue un rôle qui sera expliqué plus loin.In each of the intervals between the cathode 3 and the anodes 4 is provided a device for stirring the electrolyte which may be constituted by a dip tube 5 whose upper end is bent as shown in 6. This dip tube whose lower end is perforated to allow the entry of electrolyte in the tube, is connected a pipe 7 supplying this tube 5 with compressed air from a source of compressed air, not shown. The compressed air supplied to the lower part of the dip tube 5 is expelled in mixture with liquid fixative through the free end 6, creating permanent agitation or turbulence in the intervals between the cathode 3 and the anodes 4, so that that the silver ions in the electrolytic bath are brought close to the cathode (s) 3 in order to be fixed there. Between the cathode 3 and one of the anodes 4 is placed a control electrode 8 immersed in the electrolytic bath. This electrode which has a determined potential with respect to the cathode, plays a role which will be explained later.

La cathode 3, les deux anodes 4 et l'électrode de contrôle 8 sont reliées par des conducteurs électriques à un dispositif de commande monté dans un boîtier (non représenté) dans lequel est également monté le dispositif d'alimentation en air comprimé.The cathode 3, the two anodes 4 and the control electrode 8 are connected by electrical conductors to a control device mounted in a housing (not shown) in which is also mounted the compressed air supply device.

Le bain de fixateur photographique utilisé dans le procédé suivant l'invention est avantageusement une solution aqueuse contenant environ 100 à 200 g/1 de thiosulfate d'ammonium ou de sodium et de 0 à 50 g/1 de thiocyanate d'ammonium, ainsi qu'un excès de sulfite de sodium pouvant atteindre une concentration de 60 g/1. Ce-bain contient également un agent tannant connu, à une concentration de départ qui peut atteindre 15 g/litre, cette concentration étant habituellement comprise entre environ 5 et 15 g/litre. Le pH du bain de fixage photographique est maintenu à une valeur d'environ 3,5 à 4,5 en y ajoutant, le cas échéant, une petite quantité d'un acide, tel que l'acide acétique.The photographic fixative bath used in the process according to the invention is advantageously an aqueous solution containing approximately 100 to 200 g / l of ammonium or sodium thiosulfate and from 0 to 50 g / l of ammonium thiocyanate, as well as '' an excess of sodium sulfite up to a concentration of 60 g / 1. This bath also contains a known tanning agent, at a starting concentration which can reach 15 g / liter, this concentration usually being between approximately 5 and 15 g / liter. The pH of the photographic fixing bath is maintained at a value of approximately 3.5 to 4.5 by adding thereto, if necessary, a small amount of an acid, such as acetic acid.

11 est évident qu'au lieu de comporter une cathode 3 et deux anodes 4, la cellule d'électrolyse 1 pourrait contenir un plus grand nombre de cathodes et d'anodes, le nombre d'anodes étant toujours supérieur d'une unité au nombre de cathodes.It is obvious that instead of having a cathode 3 and two anodes 4, the electrolysis cell 1 could contain a greater number of cathodes and anodes, the number of anodes always being one unit greater than the number cathodes.

Comme on l'a signalé plus haut, le courant d'électrolyse dans la cellule d'électrolyse 1 est soumis à une régulation en fonction de la teneur en argent du bain électrolytique en sorte que le courant diminue lorsque la teneur en argent du bain électrolytique devient inférieure à une valeur faible prédéterminée, par exemple 0,5-2 g/1. Cette régulation est assurée à partir du potentiel de l'électrode de contrôle 8 par l'intermédiaire d'un dispositif de régulation 10 illustré schématiquement à la figure 2. Ce dispositif est organisé pour maintenir le potentiel Uec de l'électrode de contrôle 8 à une valeur de consigne prédéterminée et pour comparer ce potentiel au potentiel de la cathode 3 afin de régler le courant d'électrolyse. A cet effet, le potentiel Uec de l'électrode de contrôle 8 est appliqué par la ligne 103 à une borne 101 du dispositif de régulation 10. A une seconde borne 102 est appliqué le potentiel de référence ou de consigne prédéterminé Uref. Les potentiels Uec et Uref sont de polarités opposées et sont additionnés par un montage de résistances 11 : la somme de ces potentiels est appliquée à une première entrée 104 d'un amplificateur opérationnel 12. Une seconde entrée 105 de cet amplificateur reçoit le potentiel Uc de la cathode 3 par la ligne 106 à travers la résistance 13. Un condensateur d'intégration 14 se trouve connecté en parallèle avec l'amplificateur 12.As mentioned above, the electrolysis current in the electrolysis cell 1 is regulated according to the silver content of the electrolytic bath so that the current decreases when the silver content of the electrolytic bath becomes less than a predetermined low value, for example 0.5-2 g / 1. This regulation is ensured from the potential of the control electrode 8 by means of a regulation device 10 illustrated diagrammatically in FIG. 2. This device is organized to maintain the potential Uec of the control electrode 8 at a predetermined set value and to compare this potential with the potential of the cathode 3 in order to adjust the electrolysis current. To this end, the potential Uec of the control electrode 8 is applied by line 103 to a terminal 101 of the regulating device 10. To a second terminal 102 is applied the predetermined reference or reference potential Uref. The potentials Uec and Uref are of opposite polarities and are added by a circuit of resistors 11: the sum of these potentials is applied to a first input 104 of an operational amplifier 12. A second input 105 of this amplifier receives the potential Uc from the cathode 3 via the line 106 through the resistor 13. An integration capacitor 14 is connected in parallel with the amplifier 12.

Lorsque le potentiel Uec est égal au potentiel de consigne Uref en valeur absolue (ces potentiels sont de polarités opposés), le courant sur la ligne 104 est nul et la tension aux bornes du condensateur 14 se trouve à une valeur constante. La tension sur la ligne de sortie 107 de l'amplificateur 12 commande un générateur de courant 15 pour engendrer un courant qui, après amplification dans l'amplificateur 16, alimente les anodes 4 pour fournir le courant d'électrolyse.When the potential Uec is equal to the setpoint potential Uref in absolute value (these potentials are of opposite polarities), the current on line 104 is zero and the voltage across the terminals of capacitor 14 is at a constant value. The voltage on the output line 107 of the amplifier 12 controls a current generator 15 to generate a current which, after amplification in the amplifier 16, supplies the anodes 4 to supply the electrolysis current.

Lorsque le potentiel Uec devient inférieur en valeur absolue au potentiel de consigne Uref, il apparait sur la ligne 104 un courant qui charge le condensateur 14 et la tension de commande sur la ligne de sortie 107 varie; cette variation de tension a pour effet de faire varier le courant engendré par le générateur 15 et partant de réduire le courant d'électrolyse. Cette variation de courant tend à rétablir le potentiel de l'électrode de contrôle 8 et la différence de potentiel entre cette électrode et la cathode 3.When the potential Uec becomes lower in absolute value than the setpoint potential Uref, there appears on line 104 a current which charges the capacitor 14 and the control voltage on the output line 107 varies; this voltage variation has the effect of varying the current generated by the generator 15 and therefore reducing the electrolysis current. This variation in current tends to restore the potential of the control electrode 8 and the potential difference between this electrode and the cathode 3.

La loi qui régit la valeur de la différence de potentiel entre l'électrode de contrôle 8 et la ou les cathodes 3 revêtue(s) d'argent est exprimée par la relation suivante :

Figure imgb0001
dans laquelle

  • Uec est le potentiel de l'électrode de contrôle,
  • Ueco est le potentiel de l'électrode de contrôle au temps zéro,
  • [Ag) est la concentration en argent du bain au temps considéré
  • [Ag]to est la concentration en argent du bain au temps zéro.
The law which governs the value of the potential difference between the control electrode 8 and the cathode (s) 3 coated with silver is expressed by the following relation:
Figure imgb0001
 in which
  • U ec is the potential of the control electrode,
  • U eco is the potential of the control electrode at time zero,
  • [Ag) is the concentration of silver in the bath at the time considered
  • [Ag] to is the silver concentration of the bath at time zero.

Avantageusement, le potentiel de référence Uref est choisi égal au potentiel que prendrait l'électrode de contrôle 8 pour une concentration du bain électrolytique de l'ordre de 0,5 à 2g/l avec un courant d' électrolyse nul. Le potentiel de référence Uref est par exemple de 300 à 600 millivolts.Advantageously, the reference potential Uref is chosen to be equal to the potential that the control electrode 8 would take for a concentration of the electrolytic bath of the order of 0.5 to 2 g / l with a zero electrolysis current. The reference potential Uref is for example from 300 to 600 millivolts.

L'électrode de contrôle 8 est avantageusement polarisée par un faible courant, de 1 mA par exemple, pour assurer une protection de cette électrode contre une altération qui serait provoquée en surface. Cette disposition avantageuse est illustrée à la figure 2 sur laquelle on voit que l'électrode 8 est connectée à un générateur de tension 17 à travers une résistance 18.The control electrode 8 is advantageously polarized by a low current, of 1 mA for example, to protect this electrode against damage which would be caused at the surface. This advantageous arrangement is illustrated in FIG. 2 in which it can be seen that the electrode 8 is connected to a voltage generator 17 through a resistor 18.

L'électrode de contrôle 8 est protégée par une gaine 9, par exemple en mousse, pour éviter une turbulence du bain électrolytique au voisinage immédiat de cette électrode, une telle turbulence pouvant avoir pour effet de provoquer une variation indésirable du potentiel de cette électrode.The control electrode 8 is protected by a sheath 9, for example made of foam, to avoid turbulence of the electrolytic bath in the immediate vicinity of this electrode, such turbulence possibly having the effect of causing an undesirable variation in the potential of this electrode.

Il est évident que l'invention n'est pas limitée aux détails décrits plus haut à titre d'exemple.It is obvious that the invention is not limited to the details described above by way of example.

Claims (10)

1. Procédé de traitement d'un bain de fixateur photographique en vue d'en extraire l'argent sous forme métallique, dans lequel on soumet le bain de fixateur photographique agité contenant un antioxydant à une électrolyse de manière à assurer le dépôt d'argent métallique sur au moins une cathode (3) disposée entre des anodes (4), une électrode de contrôle étant disposée à proximité de la cathode, caractérisé en ce qu'on règle l'intensité du courent d'électrolyse en mesurant à la fois la résistivité de la cellule d'électrolyse et la surtension aux électrodes par la différence de potentiel entre une cathode servant d'électrode de travail (3) et l'électrode de contrôle (8).1. Process for the treatment of a photographic fixer bath with a view to extracting the silver in metallic form, in which the stirred photographic fixer bath containing an antioxidant is subjected to electrolysis so as to deposit silver metallic on at least one cathode (3) disposed between anodes (4), a control electrode being disposed near the cathode, characterized in that the intensity of the electrolysis current is adjusted by measuring both the resistivity of the electrolysis cell and overvoltage at the electrodes by the potential difference between a cathode serving as the working electrode (3) and the control electrode (8). 2. Procédé suivant la revendication 1, caractérisé en ce qu'on règle le courant d'électrolyse en fonction de la différence de potentiel entre une cathode servant d'électrode de travail (3) et l'électrode de contrôle (8), la tension de l'électrode de contrôle étant maintenue à une valeur de référence prédéterminée (Uref).2. Method according to claim 1, characterized in that the electrolysis current is adjusted as a function of the potential difference between a cathode serving as the working electrode (3) and the control electrode (8), the voltage of the control electrode being maintained at a predetermined reference value (Uref). 3. Procédé suivant l'une quelconque des revendications 1 et 2, caractérisé en ce qu'on maintient le potentiel de l'électrode de contrôle (8) à une valeur (Uref) égale à celle qu'elle prendrait dans le cas où la teneur en argent du bain électrolytique serait descendue à environ 0,5 à 2g/1, lorsque le courant d' électrolyse est nul.3. Method according to any one of claims 1 and 2, characterized in that the potential of the control electrode (8) is maintained at a value (Uref) equal to that which it would take in the case where the silver content of the electrolytic bath would have dropped to around 0.5 to 2g / 1, when the electrolysis current was zero. 4. Procédé suivant la revendication 3, caractérisé en ce qu'on maintient le potentiel de l' électrode de contrôle (8) à une valeur de référence d'environ 300 à 600 millivolts.4. Method according to claim 3, characterized in that the potential of the control electrode (8) is maintained at a reference value of approximately 300 to 600 millivolts. 5. Procédé suivant l'une quelconque des revendications 1 à 4, caractérisé en ce qu'on inhibe l'agitation du bain électrolytique au voisinage de l'électrode de contrôle.5. Method according to any one of claims 1 to 4, characterized in that the agitation of the electrolytic bath in the vicinity of the control electrode is inhibited. 6. Appareil de traitement d'un bain de fixateur photographique en vue d'en extraire l'argent sous forme métalliaue par le procédé suivant l'une quelconque des revendications précédentes, cet appareil comprenant une cellule d'électrolyse comportant, comme électrodes , au moins une cathode et des anodes ainsi qu'une électrode de contrôle, caractérisé en ce que l'électrode de contrôle (8) est composée de carbone pur et est plongée dans le bain électrolytique agité à proximité de ladite ou d'une cathode (3) servant d'électrode de travail, et en ce qu'il comprend un dispositif de régulation (10) connecté à l'électrode de contrôle et à ladite cathode et agencé pour régler le courant d'électrolyse en réponse à la différence de potentiel entre ladite électrode de contrôle et ladite cathode.6. Apparatus for treating a photographic fixer bath with a view to extracting the silver in metallic form by the method according to any one of the preceding claims, this apparatus comprising an electrolysis cell comprising, as electrodes, at less a cathode and anodes as well as a control electrode, characterized in that the control electrode (8) is composed of pure carbon and is immersed in the stirred electrolytic bath near said or of a cathode (3 ) serving as a working electrode, and in that it comprises a regulating device (10) connected to the control electrode and to said cathode and arranged to regulate the electrolysis current in response to the potential difference between said control electrode and said cathode. 7. Appareil suivant la revendication 6, caractérisé en ce que le dispositif de régulation (10) est agencé pour maintenir le potentiel de l'électrode de contrôle (8) pratiquement constant par rapport au potentiel de ladite cathode (3).7. Apparatus according to claim 6, characterized in that the regulating device (10) is arranged to maintain the potential of the control electrode (8) practically constant with respect to the potential of said cathode (3). 8. Appareil suivant l'une quelconque des revendications 6 et 7, caractérisé en ce que le dispositif de régulation (10) comprend un montage additionneur (11) connecté pour additionner le potentiel (Uec) de l'électrode de contrôle (8) et un potentiel de référence prédéterminé (Uref); un montage comparateur/intégrateur (12,14) ayant une entrée (104) connectée à la sortie du montage additionneur (11) et une seconde entrée (105) connectée pour recevoir le potentiel de ladite cathode (3), ledit montage étant agencé pour intégrer la différence de potentiel entre ladite électrode de contrôle. et le potentiel de référence et pour comparer la valeur intégrée au potentiel de la cathode en sorte de produire un signal de commande, et un générateur de courant (15,16) connecté pour fournir le courant d'électrolyse en réponse audit signal de commande du montage comparateur/intégrateur (12,14).8. Apparatus according to any one of claims 6 and 7, characterized in that the regulation device (10) comprises an adder assembly (11) connected to add the potential (Uec) of the control electrode (8) and a predetermined reference potential (Uref); a comparator / integrator assembly (12,14) having an input (104) connected to the output of the adder assembly (11) and a second input (105) connected to receive the potential of said cathode (3), said assembly being arranged to integrate the potential difference between said control electrode. and the reference potential and for comparing the integrated value with the potential of the cathode so as to produce a control signal, and a current generator (15,16) connected to supply the electrolysis current in response to said control signal of the comparator / integrator assembly (12,14). 9. Appareil suivant l'une quelconque des revendications 7 et 8, caractérisé en ce qu'il comprend un dispositif (17, 18) pour polariser l'électrode de contrôle (8).9. Apparatus according to any one of Claims 7 and 8, characterized in that it comprises a device (17, 18) for polarizing the control electrode (8). 10. Appareil suivant l'une quelconque des revendications 7 à 9, caractérisé en ce que l'électrode de contrôle (8) est munie de moyens de protection (9) évitant l'agitation du bain électrolytique au voisinage de cette électrode.10. Apparatus according to any one of claims 7 to 9, characterized in that the control electrode (8) is provided with protective means (9) preventing agitation of the electrolytic bath in the vicinity of this electrode.
EP81870013A 1980-02-21 1981-02-16 Process and apparatus for treating photographic baths Expired EP0035008B1 (en)

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FR2556374A1 (en) * 1983-12-12 1985-06-14 Joliot Robert Device for maintaining the silver concentration at a determined value in fixing baths in cinematographic or photographic laboratories
EP0201837A1 (en) * 1985-05-14 1986-11-20 Kodak-Pathe Process and apparatus for the readjustment of the operational setting in an electrolysis cell
EP0598144A1 (en) * 1992-11-10 1994-05-25 Agfa-Gevaert N.V. Use of a pH sensitive reference electrode in electrolytic desilvering
EP0754780A1 (en) * 1995-07-15 1997-01-22 Agfa-Gevaert N.V. Process for de-silvering a silver-containing solution
US5759377A (en) * 1995-07-15 1998-06-02 Agfa-Gevaert Process for de-silvering of a silver-containing solution

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US4675085A (en) * 1985-07-31 1987-06-23 Adalberto Vasquez Method and apparatus for recovery of metal from solution
GB8927964D0 (en) * 1989-12-11 1990-02-14 Kodak Ltd Method and apparatus for recovering silver from a photographic fixing solution
US5770034A (en) * 1995-07-15 1998-06-23 Agfa-Gevaert N.V. Process and apparatus for desilvering a silver-containing solution
GB9726534D0 (en) * 1997-12-17 1998-02-11 Eastman Kodak Co Determination of silver in a photographic solution

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US4065374A (en) * 1976-08-10 1977-12-27 New Nippon Electric Co., Ltd. Method and apparatus for plating under constant current density

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US4186067A (en) * 1974-06-26 1980-01-29 Ciba-Geigy Aktiengesellschaft Electrolytic recovery of silver from photographic bleach-fix baths
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US1866701A (en) * 1929-03-13 1932-07-12 Eastman Kodak Co Method and apparatus for recovering silver from fixing solutions
DE1187806B (en) * 1962-03-21 1965-02-25 Bayer Ag Process and device for the recovery of silver from fixing baths
US4065374A (en) * 1976-08-10 1977-12-27 New Nippon Electric Co., Ltd. Method and apparatus for plating under constant current density

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2556374A1 (en) * 1983-12-12 1985-06-14 Joliot Robert Device for maintaining the silver concentration at a determined value in fixing baths in cinematographic or photographic laboratories
EP0201837A1 (en) * 1985-05-14 1986-11-20 Kodak-Pathe Process and apparatus for the readjustment of the operational setting in an electrolysis cell
FR2582022A1 (en) * 1985-05-14 1986-11-21 Kodak Pathe METHOD AND DEVICE FOR REGULATING THE POSITION OF THE OPERATING POINT OF AN ELECTROLYSIS CELL
EP0598144A1 (en) * 1992-11-10 1994-05-25 Agfa-Gevaert N.V. Use of a pH sensitive reference electrode in electrolytic desilvering
EP0754780A1 (en) * 1995-07-15 1997-01-22 Agfa-Gevaert N.V. Process for de-silvering a silver-containing solution
US5759377A (en) * 1995-07-15 1998-06-02 Agfa-Gevaert Process for de-silvering of a silver-containing solution

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EP0035008B1 (en) 1985-01-30
ATE11602T1 (en) 1985-02-15
US4377456A (en) 1983-03-22
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LU82188A1 (en) 1981-09-10
JPS56138737A (en) 1981-10-29
EP0035008A3 (en) 1982-06-09

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