Patent US4740244A successfully refreshed from Google Patents.
US4740244A
Expired / Lapsed
US
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Process for recovery of silver from spent, waste, acidic processing fluids
Assignee: EIDP Inc
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Filing: 1986-10-31
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Granted: 1988-04-26
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Expires: 2006-10-31
Abstract
Abstract Process for recovery of silver from spent, waste acidic silver halide photographic processing fluid, e.g., fixer solution, comprising passing the fluid through finely divided iron, e.g., steel wool, contained in a vessel in the presence of a metal salt of copper or cadmium, e.g., copper(II)sulfate, copper chloride dihydrate, cadmium sulfate, etc. The ratio of iron to metal salt is 25 to 1 to 4 to 1. An apparatus for recovery of silver is also described.
Inventors
- 👤 James E. Williams
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 17:40
CPC Classifications
C; C22; C22B; C22B11/00; C22B11/04; C22B11/042; C22B11/046; Y; Y02; Y02P; Y02P10/00; Y02P10/20
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
92 words
A process for the recovery of silver from spent, waste acidic silver halide photographic processing fluid which comprises passing the waste processing fluid through finely divided iron contained in a vessel and recovering the fluid containing substantially no dissolved silver, the improvement wherein the vessel contains a minor amount with respect to the amount of finely divided iron of a metal salt wherein the metal is taken from the group consisting of copper and cadmium, the ratio of finely divided iron to metal salt being 25 to 1 to 4 to 1.
Claim 2
Dependent Claim
92 words
A process for the recovery of silver from spent, waste acidic silver halide photographic processing fluid which comprises passing the waste processing fluid through finely divided iron contained in a vessel and recovering the fluid containing substantially no dissolved silver, the improvement wherein the vessel contains a minor amount with respect to the amount of finely divided iron of a metal salt wherein the metal is taken from the group consisting of copper and cadmium, the ratio of finely divided iron to metal salt being 25 to 1 to 4 to 1.
Claim 3
Dependent Claim
14 words
A process according to claim 1 wherein the metal of the salt is copper.
Claim 4
Dependent Claim
14 words
A process according to claim 1 wherein the metal of the salt is cadmium.
Claim 5
Dependent Claim
12 words
A process according to claim 2 wherein the metal salt is copper(II)sulfate.
Claim 6
Dependent Claim
13 words
A process according to claim 3 wherein the metal salt is cadmium sulfate.
Claim 7
Dependent Claim
13 words
A process according to claim 2 wherein the metal salt is copper(II)chloride dihydrate.
Claim 8
Dependent Claim
16 words
A process according to claim 1 wherein the iron is in the form of steel wool.
References Cited (Backward Citations)
US2216765A
Cited
US3369801A
Cited
FR2106962A5
Cited
US3705716A
Cited
GB1353805A
Cited
US3792845A
Cited
US4213600A
Cited
US4303441A
Cited
US4441697A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-04-26 | 1991-10-26 | 1992-04-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-04-26 | 1995-10-26 | 1996-04-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-04-26 | 1999-10-26 | 2000-04-26 | $7700.00 | Window Closed / Lapsed |