US2772290A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Preparing pyrocatechin-sulfon-phthalein
Assignee: Individual
•
Filing: 1954-05-25
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Granted: 1956-11-27
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Expires: 1974-05-25
Abstract
No abstract record available.
Inventors
- 👤 Vodak Zdenek
- 👤 Leminger Otakar
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 09:01
CPC Classifications
C; C09; C09B; C09B11/00; C09B11/04; C09B11/06; C09B11/08
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
36 words
METHOD OF PREPARING PURE CRYSTALLINE PYROCATECHINSULFONPHTHALEIN, COMPRISING CONDENSING O-SULFOBENZOIC ACID ANHYDRIDE WITH PYROCATECHIN BY MELTING SAID COMPOUNDS IN EQUIMOLAR PROPORTIONS AT TEMPERATURES SUBSTANTIALLY BETWEEN 100* AND 110*C. THE CONDENSATION TAKING PLACE ACCORDING TO THE FOLLOWING EQUATION:
Claim 2
Dependent Claim
36 words
METHOD OF PREPARING PURE CRYSTALLINE PYROCATECHINSULFONPHTHALEIN, COMPRISING CONDENSING O-SULFOBENZOIC ACID ANHYDRIDE WITH PYROCATECHIN BY MELTING SAID COMPOUNDS IN EQUIMOLAR PROPORTIONS AT TEMPERATURES SUBSTANTIALLY BETWEEN 100* AND 110*C. THE CONDENSATION TAKING PLACE ACCORDING TO THE FOLLOWING EQUATION:
Claim 3
Dependent Claim
10 words
COMPLEXONOMETRIC INDICATOR CONSISTING OF PYROCATECHIN-SULFONPHTHALEIN IN A PURE CRYSTALLINE STATE.
Claim 4
Dependent Claim
10 words
COMPLEXONOMETRIC INDICATOR CONSISTING OF PYROCATECHIN-SULFONPHTHALEIN IN A PURE CRYSTALLINE STATE.
References Cited (Backward Citations)
US1786611A
Cited
US2382730A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1959-11-27 | 1960-05-28 | 1960-11-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1963-11-27 | 1964-05-28 | 1964-11-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1967-11-27 | 1968-05-28 | 1968-11-27 | $7700.00 | Window Closed / Lapsed |