US3929466A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Recovery of silver from silver salts
Assignee: GAF Corp
•
Filing: 1974-06-28
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Granted: 1975-12-30
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Expires: 1994-06-28
Abstract
Abstract A method of converting a silver salt to metallic silver, which comprises heating, to a temperature of at least about 300*C but below the melting point of silver, an admixture comprising a silver salt and an oxygen-containing alkali metal compound that will react with said silver salt at said temperature to form silver metal, for a period of time at least sufficient to convert said silver salt to metallic silver, said temperature being sufficient to initiate said conversion.
Inventors
- 👤 Edward B Moynahan
- 👤 Jr August H Brunner
- 👤 Gerald R Skreckoski
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 06:46
CPC Classifications
C; C22; C22B; C22B11/00
Claims Analysis
Total Claims: 32
Claim 1
Independent Claim
77 words
A METHOD OF CONVERTING A SILVER SALT TO METALLIC SILVER, WHICH COMPRISES HEATING, TO A TEMPERATURE OF AT LEAST ABOUT 300*C BUT BELOW THE MELTING POINT OF SILVER, AN ADMIXTURE COMPRISING A SILVER SALT AND AN OXYGEN-CONTAINING ALAKLI METAL COMPOUND THAT WILL REACT WITH SAID SALT AT SAID TEMPERATURE TO FORM SILVER METAL, FOR A PERIOD OF TIME AT LEAST SUFFICIENT TO CONVERT SAID SILVER SALT TO METALLIC SILVER, SAID TEMPERATUURE BEING SUFFICIENT TO INITIATE SAID CONVERSION.
Claim 2
Independent Claim
77 words
A METHOD OF CONVERTING A SILVER SALT TO METALLIC SILVER, WHICH COMPRISES HEATING, TO A TEMPERATURE OF AT LEAST ABOUT 300*C BUT BELOW THE MELTING POINT OF SILVER, AN ADMIXTURE COMPRISING A SILVER SALT AND AN OXYGEN-CONTAINING ALAKLI METAL COMPOUND THAT WILL REACT WITH SAID SALT AT SAID TEMPERATURE TO FORM SILVER METAL, FOR A PERIOD OF TIME AT LEAST SUFFICIENT TO CONVERT SAID SILVER SALT TO METALLIC SILVER, SAID TEMPERATUURE BEING SUFFICIENT TO INITIATE SAID CONVERSION.
Claim 3
Dependent Claim
19 words
The method according to claim 1, wherein said heating at said temperature is for at least about 30 minutes.
Claim 4
Dependent Claim
32 words
The method according to claim 1, wherein said heating at said temperature is for a period of time sufficient to convert at least about 90% of said silver salt to metallic silver.
Claim 5
Dependent Claim
15 words
The method according to claim 1, wherein Said temperature is about 400* to about 950*C.
Claim 6
Dependent Claim
27 words
The method according to claim 1, wherein the molar ratio of said alkali metal compound to said silver salt is from about 0.4: 1 to about 5.0:1.
Claim 7
Dependent Claim
32 words
The method according to claim 1, wherein said silver salt is selected from the group consisting of a silver halide, sulfide, sulfate, and thiosulfate, and a mixture of two or more thereof.
Claim 8
Dependent Claim
20 words
The method according to claim 6, wherein said silver salt is a silver halide or a mixture of silver halides.
Claim 9
Dependent Claim
35 words
The method according to claim 1, wherein said alkali metal compound is selected from the group consisting of an alkali metal carbonate, bicarbonate, hydroxide, nitrate, and sulfate and a mixture of two or more thereof.
Claim 10
Dependent Claim
16 words
The method according to claim 8, wherein said alkali metal compound is an alkali metal carbonate.
Claim 11
Dependent Claim
16 words
The method according to claim 8, wherein said alkali metal compound is an alkali metal hydroxide.
Claim 12
Dependent Claim
24 words
The method according to claim 8, wherein said alkali metal compound is a mixture of an alkali metal carbonate and an alkali metal hydroxide.
Claim 13
Dependent Claim
16 words
The method according to claim 8, wherein said alkali metal compound is an alkali metal nitrate.
Claim 14
Dependent Claim
24 words
The method according to claim 8, wherein said alkali metal compound is a mixture of an alkali metal carbonate and an alkali metal nitrate.
Claim 15
Dependent Claim
34 words
The method according to claim 1, wherein said metallic silver thus formed is melted by heating the reaction mixture above the melting point of silver, and molten silver is separated from the reaction mass.
Claim 16
Independent Claim
83 words
A method of recovering silver metal from photographic waste material comprising at least one silver salt, which comprises heating the waste material to a temperature of at least about 300*C but below the melting point of silver, in admixture with an oxygen-containing alkali metal compound that will react with said silver salt at said temperature to form silver metal, for a period of time at least sufficient to convert said silver salt to metallic silver, said temperature being sufficient to initiate said conversion.
Claim 17
Independent Claim
83 words
A method of recovering silver metal from photographic waste material comprising at least one silver salt, which comprises heating the waste material to a temperature of at least about 300*C but below the melting point of silver, in admixture with an oxygen-containing alkali metal compound that will react with said silver salt at said temperature to form silver metal, for a period of time at least sufficient to convert said silver salt to metallic silver, said temperature being sufficient to initiate said conversion.
Claim 18
Dependent Claim
43 words
The method according to claim 15, wherein said waste material comprises gelatin, and said waste material is pretreated prior to said heating by reacting the waste material with an acid in an amount to degrade at least a substantial portion of said gelatin.
Claim 19
Dependent Claim
26 words
The method according to claim 16, wherein said acid is in an amount of from about 2% to about 30% by weight of said waste material.
Claim 20
Dependent Claim
27 words
The method according to claim 17, wherein the waste material is filtered after said acid pretreatment, and the solids thus obtained are subjected to said heating step.
Claim 21
Dependent Claim
49 words
The method according to claim 17, wherein the waste material is filtered after said acid pretreatment, and the solids thus obtained are ignited at an elevated temperature below the melting point of silver to burn off organic material in the solids prior to subjecting the solids to said heating.
Claim 22
Dependent Claim
63 words
The method according to claim 17, wherein the waste material is filtered after said acid pretreatment, and the solids thus obtained are admixed with said alkali metal compound, the admixture thus obtained being first ignited at an elevated temperature below the melting point of silver to burn off organic material in the solids and then the remaining admixture is subjected to said heating.
Claim 23
Dependent Claim
15 words
The method according to claim 15, wherein said waste material comprises photographic silver halide emulsion.
Claim 24
Dependent Claim
23 words
The method according to claim 15, wherein said waste material comprises a waste solution obtained from the manufacture or processing of photographic materials.
Claim 25
Dependent Claim
19 words
The method according to claim 22, wherein said waste solution is a spent fixing bath or a wash liquid.
Claim 26
Dependent Claim
19 words
The method according to claim 15, wherein said heating at said temperature is for at least about 30 minutes.
Claim 27
Dependent Claim
32 words
The method according to claim 15, wherein said heating at said temperature is for a period of time sufficient to conVert at least about 90% of said silver salt to metallic silver.
Claim 28
Dependent Claim
15 words
The method according to claim 15, wherein said temperature is about 400* to about 950*C.
Claim 29
Dependent Claim
27 words
The method according to claim 15, wherein the molar ratio of said alkali metal compound to said silver salt is from about 0.4: 1 to about 5.0:1.
Claim 30
Dependent Claim
32 words
The method according to claim 15, wherein said silver salt is selected from the group consisting of a silver halide, sulfide, sulfate, and thiosulfate, and a mixture of two or more thereof.
Claim 31
Dependent Claim
35 words
The method according to claim 15, wherein said alkali metal compound is selected from the group consisting of an alkali metal carbonate, bicarbonate, hydroxide, nitrate, and sulfate and a mixture of two or more thereof.
Claim 32
Dependent Claim
34 words
The method according to claim 15, wherein said metallic silver thus formed is melted by heating the reaction mixture above the melting point of silver, and molten silver is separated from the reaction mass.
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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) | 1978-12-29 | 1979-06-30 | 1979-12-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-12-29 | 1983-06-30 | 1983-12-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-12-29 | 1987-06-30 | 1987-12-30 | $7700.00 | Window Closed / Lapsed |