Patent US7280529B1 successfully refreshed from Google Patents.
US2825698A
Expired / Lapsed
US
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Method for the preparation of density gradients
Assignee: Dow Chemical Co
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Filing: 1955-12-27
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Granted: 1958-03-04
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Expires: 1975-12-27
Abstract
No abstract record available.
Inventors
- 👤 William C Taylor
- 👤 Tung Lu Ho
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 12:00
CPC Classifications
G; G01; G01N; G01N9/00; G01N9/10
Claims Analysis
Total Claims: 1
Claim 1
Independent Claim
109 words
METHOD FOR PREPARING A DENSITY GRADIENT CONSISTING OF A UNIFORMLY VARYING MIXTURE OF TWO MISCIBLE AND COMPATIBLE LIQUIDS HAVING DIFFERENT DENSITIES WHICH COMPRISES CONTINUOUSLY INCORPORATING, AT A UNIFORM RATE, A FIRST LIQUID HAVING A GIVEN DENSITY IN A MIXTURE MAINTAINED AT A SUBSTANTIALLY CONSTANT VOLUME WITH A SECOND LIQUID WHICH HAS A DENSITY DIFFERENT THAN THE FIRST LIQUID SO AS TO CONSTANTLY CHANGE THE DENSITY OF THE MIXTURE; AND CONTINUOUSLY TRANSFERRING, WITHOUT TURBULENCE, PORTIONS OF THE CONSTANTLY CHANGING DENSITY MIXTURE TO FILL A LIQUID DENSITY GRADIENT COLUMN IN A COLUMNAR CONTAINER AT ABOUT THE SAME UNIFORM RATE AS THAT AT WHICH THE FIRST LIQUID IS ADDED TO THE MIXTURE.
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) | 1961-03-03 | 1961-09-02 | 1962-03-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1965-03-03 | 1965-09-02 | 1966-03-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1969-03-03 | 1969-09-02 | 1970-03-04 | $7700.00 | Window Closed / Lapsed |