Patent DE477741C successfully refreshed from Google Patents.
US4065313A
Expired / Lapsed
US
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Bleach-fix regeneration monitoring method
Assignee: Eastman Kodak Co
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Filing: 1976-06-11
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Granted: 1977-12-27
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Expires: 1996-06-11
Abstract
Abstract A monitoring technique for use in the regeneration of spent bleach-fix solution containing silver ion and ferrous ion resulting from photograhic processing. Regeneration comprises first treating the spent solution with elemental iron to reduce and chemically replace silver ion, and thereafter dispersing an oxidizing agent throughout the silver-free solution to convert ferrous ion to ferric ion. Exhaustion of the elemental iron in the silver replacement step or insufficient oxidation in the ferrous-ferric conversion step are electrochemically detected by comparison of the half-cell potential of a reference solution drawn from the bleach-fix solution in a region of the regenerative cycle where the solution is substantially insensitive to the exhaustion of the elemental iron and insufficient oxidation. Further provision of a continuously flushing reference solution provides longterm accuracy of the electrochemical monitoring method.
Inventors
- 👤 Frederick Lee Shippey
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 16:38
CPC Classifications
G; G03; G03C; G03C5/00; G03C5/26; G03C5/395; G03C5/3952; G03D; G03D3/00; G03D3/02; G03D3/06; G03D3/065
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
216 words
In a process for regenerating a spent bleach-fix photographic solution to restore its bleaching capability and thereby permit its reuse in photographic processing, the bleaching agent being a ferric complex of an aminopolycarboxylic acid, the spent bleach-fix solution comprising silver ion and ferrous ion as a result of its use in a bleach-fix step of photographic processing which process of regeneration comprises in series a first silver replacement step in which silver ion in the spent bleach-fix solution is chemically replaced by reduction using elemental iron, and an oxidation step in which ferrous ion in the spent bleach-fix solution is oxidized to ferric ion; the improvement comprising monitoring said regeneration process by electrochemically comparing the half-cell potential of the ferric-ferrous couple in a sample of the bleach-fix solution drawn from either said first silver replacement step or said oxidation step, with the half-cell potential of the ferric-ferrous ion couple in a reference solution drawn from a region of said regeneration process in which the bleach-fix solution is substantially insensitive to exhaustion of said elemental iron and insufficient oxidation, whereby either exhaustion of said elemental iron is detected when said sample bleach-fix solution is drawn from said first silver replacement step or insufficient oxidation is detected when said sample bleach-fix solution is drawn from said oxidation step.
Claim 2
Dependent Claim
216 words
In a process for regenerating a spent bleach-fix photographic solution to restore its bleaching capability and thereby permit its reuse in photographic processing, the bleaching agent being a ferric complex of an aminopolycarboxylic acid, the spent bleach-fix solution comprising silver ion and ferrous ion as a result of its use in a bleach-fix step of photographic processing which process of regeneration comprises in series a first silver replacement step in which silver ion in the spent bleach-fix solution is chemically replaced by reduction using elemental iron, and an oxidation step in which ferrous ion in the spent bleach-fix solution is oxidized to ferric ion; the improvement comprising monitoring said regeneration process by electrochemically comparing the half-cell potential of the ferric-ferrous couple in a sample of the bleach-fix solution drawn from either said first silver replacement step or said oxidation step, with the half-cell potential of the ferric-ferrous ion couple in a reference solution drawn from a region of said regeneration process in which the bleach-fix solution is substantially insensitive to exhaustion of said elemental iron and insufficient oxidation, whereby either exhaustion of said elemental iron is detected when said sample bleach-fix solution is drawn from said first silver replacement step or insufficient oxidation is detected when said sample bleach-fix solution is drawn from said oxidation step.
Claim 3
Dependent Claim
44 words
The process of claim 1 further comprising a standby silver replacement step between said first silver replacement step and said oxidation step, and wherein said reference solution is drawn from the bleach-fix solution from either said bleach-fix step or said standby silver replacement step.
Claim 4
Dependent Claim
21 words
The process of claim 2 wherein said reference solution is drawn from the bleach-fix solution from said standby silver replacement step.
Claim 5
Dependent Claim
32 words
The process of claim 1 wherein fresh reference solution is flushed through a reference sensing region, whereby the reference half-cell potential is immunized from ions drifting between said reference and sample solutions.
Claim 6
Dependent Claim
45 words
The process of claim 4 further comprising a standby silver replacement step of iron between said first silver replacement step and said oxidation step, and wherein said reference solution is drawn from the bleach-fix solution from either said bleach-fix step or standby silver replacement step.
Claim 7
Dependent Claim
21 words
The process of claim 5 wherein said reference solution is drawn from the bleach-fix solution from said standby silver replacement step.
Claim 8
Dependent Claim
33 words
The process of claim 5 wherein an error display is caused when the comparison of said sample half-cell and reference half-cell potentials reaches a level indicative of elemental iron exhaustion or insufficient oxidation.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-12-26 | 1981-06-27 | 1981-12-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-12-26 | 1985-06-27 | 1985-12-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-12-26 | 1989-06-27 | 1989-12-27 | $7700.00 | Window Closed / Lapsed |