US4003985A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Production of sodium sulfite
Assignee: Hmc Patents Holding Co Inc
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Filing: 1976-01-30
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Granted: 1977-01-18
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Expires: 1996-01-30
Abstract
Abstract Anhydrous sodium sulfite is made by a process involving introducing substantially anhydrous sodium carbonate concurrently with sulfur dioxide-containing gas into a saturated solution of sodium sulfite maintained at pH of between about 6.5 and about 7.6 at temperature above about 35 DEG C. to form a slurry of anhydrous sodium sulfite crystals, and withdrawing the crystals from the slurry. The process is initiated using a concentrated sodium sulfite solution containing less than about 3 ppm of dissolved iron.
Inventors
- 👤 Robert Joel Hoffman
- 👤 Samuel Louis Bean
- 👤 Philip Seeling
- 👤 James William Swaine, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 06:52
CPC Classifications
C; C01; C01D; C01D5/00; C01D5/14
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
118 words
The method of producing anhydrous sodium sulfite comprising: a. forming a saturated aqueous solution of sodium sulfite containing less than about 3 ppm of dissolved iron, basis the solution, and adjusting the pH of said solution to within the range of from about 6.5 to about 7.6; b. introducing into said solution substantially anhydrous sodium carbonate concurrently with a sulfur dioxide-containing gas stream, so proportioned with respect to each other as to maintain the pH of said solution within the range of from about 6.5 to about 7.6, while maintaining the temperature of said solution above about 35° C. to form a slurry of anhydrous sodium sulfite crystals; and c. withdrawing anhydrous sodium sulfite crystals from said slurry.
Claim 2
Independent Claim
118 words
The method of producing anhydrous sodium sulfite comprising: a. forming a saturated aqueous solution of sodium sulfite containing less than about 3 ppm of dissolved iron, basis the solution, and adjusting the pH of said solution to within the range of from about 6.5 to about 7.6; b. introducing into said solution substantially anhydrous sodium carbonate concurrently with a sulfur dioxide-containing gas stream, so proportioned with respect to each other as to maintain the pH of said solution within the range of from about 6.5 to about 7.6, while maintaining the temperature of said solution above about 35° C. to form a slurry of anhydrous sodium sulfite crystals; and c. withdrawing anhydrous sodium sulfite crystals from said slurry.
Claim 3
Dependent Claim
22 words
The method of claim 1 wherein the saturated aqueous solution of sodium sulfite contains less than about 1 ppm of dissolved iron.
Claim 4
Dependent Claim
25 words
The method of claim 1 wherein in step (b) the pH of the solution is maintained within the range of from about 7.0 to 7.5.
Claim 5
Dependent Claim
22 words
The method of claim 1 wherein in step (b) the temperature of the solution is maintained between about 50° and 80° C.
Claim 6
Dependent Claim
13 words
The method of claim 1 wherein the sodium carbonate is dense soda ash.
Claim 7
Dependent Claim
26 words
The method of claim 1 wherein in step (b) the pH of the solution is maintained within the range of from about 7.25 to about 7.45.
Claim 8
Dependent Claim
22 words
The method of claim 1 wherein the saturated aqueous solution of sodium sulfite contains less than about 2 ppm of dissolved iron.
Claim 9
Dependent Claim
35 words
The method of claim 7 wherein the sodium carbonate is dense soda ash, and wherein in step (b) the pH of the solution is maintained within the range of from about 7.25 to about 7.45.
Claim 10
Dependent Claim
22 words
The method of claim 8 wherein in step (b) the temperature of the solution is maintained between about 50° and 80° C.
Claim 11
Dependent Claim
67 words
The method of claim 1 wherein the saturated aqueous solution of sodium sulfite contains less than about 1 ppm of dissolved iron, wherein the sodium carbonate is dense soda ash, and wherein in step (b) the pH of the solution is maintained within the range of from about 7.25 to about 7.45, and the temperature of the solution is maintained between about 50° and about 80° C.
Claim 12
Dependent Claim
72 words
The method of claim 1 wherein the saturated solution of sodium sulfite containing less than about 3 ppm of dissolved iron has been obtained by evaporating water from an aqueous solution of sodium sulfite containing in excess of about 3 ppm of dissolved iron, basis the solution, at temperature above about 35° C. to cause precipitation of anhydrous sodium sulfite crystals therefrom, and separating the anhydrous sodium sulfite crystals from the solution.
References Cited (Backward Citations)
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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) | 1980-01-18 | 1980-07-19 | 1981-01-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-01-18 | 1984-07-19 | 1985-01-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-01-18 | 1988-07-19 | 1989-01-18 | $7700.00 | Window Closed / Lapsed |