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Patent US4108680A successfully refreshed from Google Patents.
US4108680A
Expired / Lapsed
US
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Process for removing calcium oxalate scale
Assignee: US Filter Zimpro Inc
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Filing: 1977-03-16
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Granted: 1978-08-22
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Expires: 1997-03-16
Abstract
Abstract A mixture of nitric acid and manganese dioxide is effective in removing calcium oxalate scale from metal surfaces.
Inventors
- 👤 James W. Barr, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 23:08
CPC Classifications
C; C23; C23G; C23G1/00; C23G1/02
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
86 words
A process for removing calcium oxalate scale from a metal surface of an apparatus used for thermal treatment of aqueous solutions and suspensions which comprises contacting said scale with an aqueous suspension containing from 3% to 25% by weight of nitric acid and from 1% to 10% by weight of manganese dioxide, at a temperature between 20° C. and 95° C., said metal surface being one for which the rate of corrosion caused by said suspension is less than about 30 mils of penetration per year.
Claim 2
Dependent Claim
86 words
A process for removing calcium oxalate scale from a metal surface of an apparatus used for thermal treatment of aqueous solutions and suspensions which comprises contacting said scale with an aqueous suspension containing from 3% to 25% by weight of nitric acid and from 1% to 10% by weight of manganese dioxide, at a temperature between 20° C. and 95° C., said metal surface being one for which the rate of corrosion caused by said suspension is less than about 30 mils of penetration per year.
Claim 3
Dependent Claim
14 words
A process according to claim 1 wherein the metal is stainless steel or titanium.
Claim 4
Dependent Claim
30 words
A process according to claim 1 wherein additional nitric acid and manganese dioxide are added at selected time intervals to restore the original concentrations of nitric acid and manganese dioxide.
Claim 5
Dependent Claim
26 words
A process according to claim 1 wherein the nitric acid content is about 5% by weight and the manganese dioxide content is about 2% by weight.
References Cited (Backward Citations)
DE568532C
Cited
US2132511A
Cited
US2774694A
Cited
US3369935A
Cited
US3449164A
Cited
US3518204A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-08-21 | 1982-02-20 | 1982-08-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-08-21 | 1986-02-20 | 1986-08-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-08-21 | 1990-02-20 | 1990-08-22 | $7700.00 | Window Closed / Lapsed |