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Patent US3878059A successfully refreshed from Google Patents.
US3878059A
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Method of chelometric titration of metal cations using tungsten bronze electrode
Assignee: Iowa State University Research Foundation Inc
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Filing: 1974-05-28
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Granted: 1975-04-15
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Expires: 1994-05-28
Abstract
Abstract A chelating agent of known concentration is added to a solution containing an unknown quantity of a metal cation. An electrode formed from an alkali metal tungsten bronze crystal is placed in the solution together with a reference electrode and the potential difference between the two is measured. At the end point of the titration, an abrupt and substantial negative potential shift is observed at the tungsten bronze electrode. Reverse titrations are also possible with these electrodes.
Inventors
- 👤 Margaret A Wechter
- 👤 Paul B Hahn
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 23:02
CPC Classifications
G; G01; G01N; G01N31/00; G01N31/16; G01N31/162; G01N31/164
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
127 words
IN A METHOD OF CHELOMETRIC TITRATION OF A KNOW VOLUME OF SOLUTION CONTAINING AN UNKNOWN CONCENTRATION OF A METAL ION, THE STEPS COMPRISING: CONTACTING THE SOLUTION WITH AN INDICATING ELECTRODE COMPRISING A TUNGSTEN BRONZE CRYSTAL OF THE FORMULA AXWO3 WHEREIN A IS AN ALKALI METAL AND X IS GREATER THAN 0 AND LESS 1; CONTACTING SAID SOLUTION WITH A REFERENCE ELECTRODE; ADDING A CHELATING AGENT OF KNOWN CONCENTRATION IN MEASURED VOLUME TO SAID SOLUTION TO COMPLEX SAID METAL ION, SAID CHELATING AGENT BEING A POLYCARBOXYLATE DERIVATIVE OF AN ORGANIC AMINE AND SAID INDICATING ELECTRODE BEING RESPONSIVE TO THE PRESENCE OF SAID CHELATING AGENT; AND MEASURING THE VOLTAGE BETWEEN SAID ELECTRODES, AN ABRUPT AND SUBSTANTIAL CHANGE IN SAID VOLTAGE BEING REPRESENTATIVE OF THE EQUIVALENCE POINT OF SAID TITRATION.
Claim 2
Dependent Claim
127 words
IN A METHOD OF CHELOMETRIC TITRATION OF A KNOW VOLUME OF SOLUTION CONTAINING AN UNKNOWN CONCENTRATION OF A METAL ION, THE STEPS COMPRISING: CONTACTING THE SOLUTION WITH AN INDICATING ELECTRODE COMPRISING A TUNGSTEN BRONZE CRYSTAL OF THE FORMULA AXWO3 WHEREIN A IS AN ALKALI METAL AND X IS GREATER THAN 0 AND LESS 1; CONTACTING SAID SOLUTION WITH A REFERENCE ELECTRODE; ADDING A CHELATING AGENT OF KNOWN CONCENTRATION IN MEASURED VOLUME TO SAID SOLUTION TO COMPLEX SAID METAL ION, SAID CHELATING AGENT BEING A POLYCARBOXYLATE DERIVATIVE OF AN ORGANIC AMINE AND SAID INDICATING ELECTRODE BEING RESPONSIVE TO THE PRESENCE OF SAID CHELATING AGENT; AND MEASURING THE VOLTAGE BETWEEN SAID ELECTRODES, AN ABRUPT AND SUBSTANTIAL CHANGE IN SAID VOLTAGE BEING REPRESENTATIVE OF THE EQUIVALENCE POINT OF SAID TITRATION.
Claim 3
Dependent Claim
13 words
The method of claim 1 wherein said indicating electrode is sodium tungsten bronze.
Claim 4
Dependent Claim
13 words
The method of claim 2 wherein said value of x is approximately 0.65.
Claim 5
Dependent Claim
22 words
The method of claim 1 wherein said alkali metal is seLected from the group consisting of Rb, K, Cs, Li, and Na.
Claim 6
Dependent Claim
30 words
The method of claim 1 wherein said metal ion is a divalent ion and said metal is selected from the group consisting of Ca, Mg, Zn, Ni, Cd, and Mn.
Claim 7
Dependent Claim
52 words
The method of claim 1 wherein said metal ion is selected from the group consisting of Pb(II), Fe(III), and Al(III), and wherein said method further comprises adding excess amount of chelating agent and then adding a second metal, in measured amount, to complex the excess amount of chelating agent for reverse titration.
Claim 8
Dependent Claim
21 words
The method of claim 1 wherein said chelating agent is selected from the group consisting of EDTA, EGTA, DPTA, and NTA.
Claim 9
Dependent Claim
112 words
In a method of chelometric titration, the steps comprising providing a known volume of a solution containing an unknown concentration of a divalent metal ion selected from the group consisting of calcium, magnesium, nickel, manganese, copper, cadmium, cobalt, zinc and lead; contacting said solution with an indicating electrode and a measuring electrode, said indicating electrode being a sodium tungsten bronze crystal; having a measured volume of known concentration of a polycarboxylate derivative of an organic amine to complex said metal ion; measuring the voltage between said electrode; and recording the amount of said complexing material when said voltage exhibits an abrupt and substantial change representative of the equivalence point of said titration.
Claim 10
Dependent Claim
112 words
In a method of chelometric titration, the steps comprising providing a known volume of a solution containing an unknown concentration of a divalent metal ion selected from the group consisting of calcium, magnesium, nickel, manganese, copper, cadmium, cobalt, zinc and lead; contacting said solution with an indicating electrode and a measuring electrode, said indicating electrode being a sodium tungsten bronze crystal; having a measured volume of known concentration of a polycarboxylate derivative of an organic amine to complex said metal ion; measuring the voltage between said electrode; and recording the amount of said complexing material when said voltage exhibits an abrupt and substantial change representative of the equivalence point of said titration.
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) | 1978-04-14 | 1978-10-14 | 1979-04-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-14 | 1982-10-14 | 1983-04-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-14 | 1986-10-14 | 1987-04-15 | $7700.00 | Window Closed / Lapsed |