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US3855150A
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Stabilization of hydroquinone solutions with citric acid
Assignee: Eastman Kodak Co
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Filing: 1973-03-26
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Granted: 1974-12-17
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Expires: 1993-03-26
Abstract
Abstract Solutions of hydroquinone are stabilized against deterioration in color and odor with age by the addition to the solution of small amounts of citric acid. Up to about 1 percent citric acid by weight of the solution may be used, although it is preferred that this amount be between 0.005 percent and 0.05 percent.
Inventors
- 👤 A Weris
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 06:11
CPC Classifications
C; C07; C07C; C07C37/00; C07C37/68; C07C37/88
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
51 words
THE METHOD OF STABILIZING HYDROQUINONE SOLUTIONS COMPRISING HYDROQUINONE AND A SOLVENT THEREFOR, SAID SOLVENT BEING SUBSTANTIALLY FREE FROM IMPURITIES AGAINST THE FORMATION OF UNDESIRABLE COLOR AND ODOR DURING STORAGE WHICH COMPRISES ADDING TO SAID SOLUTION FROM ABOUT 0.0025 PERCENT TO ABOUT 1 PERCENT BY WEIGHT OF THE SOLUTION OF CITRIC ACID.
Claim 2
Independent Claim
51 words
THE METHOD OF STABILIZING HYDROQUINONE SOLUTIONS COMPRISING HYDROQUINONE AND A SOLVENT THEREFOR, SAID SOLVENT BEING SUBSTANTIALLY FREE FROM IMPURITIES AGAINST THE FORMATION OF UNDESIRABLE COLOR AND ODOR DURING STORAGE WHICH COMPRISES ADDING TO SAID SOLUTION FROM ABOUT 0.0025 PERCENT TO ABOUT 1 PERCENT BY WEIGHT OF THE SOLUTION OF CITRIC ACID.
Claim 3
Dependent Claim
28 words
The method according to claim 1 which comprises adding to said solution between about 0.005 percent and about 0.05 percent by weight of the solution of citric acid.
Claim 4
Independent Claim
57 words
The method of stabilizing solutions consisting essentially of hydroquinone and a solvent therefor selected from the group consisting of ethylene glycol, diethylene glycol and methoxyethanol against the formation of undesirable color and odor during storage which comprises adding to said solution from about 0.0025 percent to about 1 percent by weight of the solution of citric acid.
Claim 5
Independent Claim
57 words
The method of stabilizing solutions consisting essentially of hydroquinone and a solvent therefor selected from the group consisting of ethylene glycol, diethylene glycol and methoxyethanol against the formation of undesirable color and odor during storage which comprises adding to said solution from about 0.0025 percent to about 1 percent by weight of the solution of citric acid.
Claim 6
Dependent Claim
28 words
The method according to claim 3 which comprises adding to said solution between about 0.005 percent and about 0.05 percent, by weights of the solution, of citric acid.
Claim 7
Independent Claim
44 words
The method of stabilizing hydroquinone solutions consisting essentially of hydroquinone and methoxyethanol against the formation of undesirable color and odor during storage which comprises adding to said solution from about 0.0025 percent to about 1 percent by weight of the solution of citric acid.
Claim 8
Independent Claim
44 words
The method of stabilizing hydroquinone solutions consisting essentially of hydroquinone and methoxyethanol against the formation of undesirable color and odor during storage which comprises adding to said solution from about 0.0025 percent to about 1 percent by weight of the solution of citric acid.
References Cited (Backward Citations)
US2607745A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-12-16 | 1978-06-17 | 1978-12-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-12-16 | 1982-06-17 | 1982-12-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-12-16 | 1986-06-17 | 1986-12-17 | $7700.00 | Window Closed / Lapsed |