US4021264A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of dissolving a silver coating in a photo tank
Assignee: Evonik Operations GmbH
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Filing: 1975-10-20
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Granted: 1977-05-03
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Expires: 1995-10-20
Abstract
Abstract Silver coatings in photographic tanks are dissolved with an aqueous solution of an alkali mono or di peroxysulfate, an alkali bisulfate and thiourea.
Inventors
- 👤 Helmut Knorre
- 👤 Joachim Fischer
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 22:17
CPC Classifications
G; G03; G03C; G03C11/00; G03C11/005
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
73 words
A process for the removal of the silver coating of a silver coated container comprising dissolving the coating by adding to the container and in contact with said coating an aqueous solution containing (a) 10-150 g/l of a member of the group consisting of an alkali peroxymonosulfate, an alkali peroxydisulfate and a mixture of an alkali peroxymonosulfate and an alkali peroxydisulfate, (b) 20-200 g/l of alkali bisulfate and (c) 5-100 g/l of thiourea.
Claim 2
Dependent Claim
73 words
A process for the removal of the silver coating of a silver coated container comprising dissolving the coating by adding to the container and in contact with said coating an aqueous solution containing (a) 10-150 g/l of a member of the group consisting of an alkali peroxymonosulfate, an alkali peroxydisulfate and a mixture of an alkali peroxymonosulfate and an alkali peroxydisulfate, (b) 20-200 g/l of alkali bisulfate and (c) 5-100 g/l of thiourea.
Claim 3
Dependent Claim
23 words
A process according to claim 1 wherein (a) comprises potassium peroxymonosulfate, sodium ammonium peroxymonosulfate, sodium peroxymonosulfate, potassium peroxydisulfate, sodium peroxydisulfate or ammonium peroxydisulfate.
Claim 4
Dependent Claim
14 words
A process according to claim 2 wherein (b) is sodium bisulfate or potassium bisulfate.
Claim 5
Dependent Claim
19 words
A process according to claim 1 including adding to the aqueous solution 5-30 grams per liter of sodium sulfate.
Claim 6
Dependent Claim
23 words
A process according to claim 1 wherein there is employed 10-40 g/l of (a), 100-180 g/l of (b) and 25-60 g/l of (c).
Claim 7
Dependent Claim
20 words
A process according to claim 5 wherein the aqueous solution consists essentially of water, (a), (b), (c) and sodium sulfate.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-05-02 | 1980-11-01 | 1981-05-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-05-02 | 1984-11-01 | 1985-05-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-05-02 | 1988-11-01 | 1989-05-03 | $7700.00 | Window Closed / Lapsed |