US4115312A
Expired / Lapsed
US
⏱️ 0.0 years remaining
X-ray fluorescent luminescent cadmium tungstate compositions
Assignee: Merck Patent GmbH
•
Filing: 1977-05-05
•
Granted: 1978-09-19
•
Expires: 1997-05-05
Abstract
Abstract In a process for producing x-ray fluorescent luminescent cadmium tungstate material by precipitation of cadmium tungstate from an aqueous solution of an alkali metal tungstate by the addition of an aqueous solution of a cadmium salt and separation, washing, drying and calcining of the resulting precipitate, an improvement is provided wherein (a) each of the alkali metal tungstate and cadmium salt solutions is at least 1N, (b) mixing of the two solutions is done over 0.1 to 4 hours, (c) approximately equivalent amounts of both solutions are mixed, (d) mixing is done at a temperature of 0° C - the boiling point of the mixture, (e) the precipitate is activated by calcination at a temperature between 400° and 1200° C for up to 6 hours, and (f) the thus-activated precipitate is reslurried in water, washed and dried.
Inventors
- 👤 Gerhard Engel
- 👤 Manfred Eckle
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 16:39
CPC Classifications
G; G03; G03C; G03C5/00; G03C5/16; G03C5/17; G21; G21K; G21K4/00
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
134 words
In a process for producing x-ray fluorescent luminescent cadmium tungstate material by precipitation of cadmium tungstate from an aqueous solution of an alkali metal tungstate by the addition of an aqueous solution of a cadmium salt and separation, washing, drying and calcining of the resulting precipitate, the improvement wherein (a) each of the alkali metal tungstate and cadmium salt solutions is at least 1N, (b) mixing of the two solutions is done over 0.1 to 4 hours, (c) approximately equivalent amounts of both solutions are mixed, (d) mixing is done at a temperature of 0° C the boiling point of the mixture (e) the precipitate is activated by calcination at a temperature between 400° and 1200° C. for up to 6 hours, and (f) the thus-activated precipitate is reslurried in water, washed and dried.
Claim 2
Dependent Claim
134 words
In a process for producing x-ray fluorescent luminescent cadmium tungstate material by precipitation of cadmium tungstate from an aqueous solution of an alkali metal tungstate by the addition of an aqueous solution of a cadmium salt and separation, washing, drying and calcining of the resulting precipitate, the improvement wherein (a) each of the alkali metal tungstate and cadmium salt solutions is at least 1N, (b) mixing of the two solutions is done over 0.1 to 4 hours, (c) approximately equivalent amounts of both solutions are mixed, (d) mixing is done at a temperature of 0° C the boiling point of the mixture (e) the precipitate is activated by calcination at a temperature between 400° and 1200° C. for up to 6 hours, and (f) the thus-activated precipitate is reslurried in water, washed and dried.
Claim 3
Dependent Claim
20 words
The process of claim 1, wherein the alkali metal tungstate is sodium tungstate and the cadmium salt is cadmium chloride.
Claim 4
Dependent Claim
21 words
The process of claim 1, wherein mixing of the alkali metal tungstate and the cadmium salt is done over 3-4 hours.
Claim 5
Dependent Claim
24 words
The process of claim 1, wherein mixing of the alkali metal tungstate and the cadmium salt is done at room temperature to 80° C.
Claim 6
Dependent Claim
15 words
The process of claim 1, wherein the precipitate is activated by calcination at 600°-700° C.
Claim 7
Dependent Claim
53 words
The process of claim 1, wherein the thus-precipitated slurry of cadmium tungstate is mixed with 0.01 to 4 mol of a mineralizer salt selected from sodium, potassium and cadmium chloride or sulfate per mol of cadmium tungstate in the slurry, dried, calcined at 400°-600° C, reslurried, washed and subsequently activated at 600°-1200° C.
Claim 8
Dependent Claim
51 words
The process of claim 1, wherein the alkali metal tungstate is sodium tungstate and the cadmium salt is cadmium chloride, mixing of the Na 2 WO 4 and CdCl 2 is done over 3-4 hours at room temperature to 80° C. and the precipitate is activated by calcination at 600°-700° C.
Claim 9
Dependent Claim
83 words
The process of claim 1, wherein the alkali metal tungstate is sodium tungstate and the cadmium salt is cadmium chloride, mixing of the Na 2 WO 4 and CdCl 2 is done over 3-4 hours at room temperature to 80° C., the thus-precipitated slurry of cadmium tungstate is mixed with 0.01 to 4 mol of sodium, potassium or cadmium chloride or sulfate per mol of cadmium tungstate in the slurry, dried, calcined at 400°-600° C., reslurried, washed and subsequently activated at 600°-1200° C.
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) | 1981-09-18 | 1982-03-20 | 1982-09-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-09-18 | 1986-03-20 | 1986-09-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-09-18 | 1990-03-20 | 1990-09-19 | $7700.00 | Window Closed / Lapsed |