Title of Invention

DEVICE FOR CONDUCTING ELECTROCHEMICAL MEASUREMENTS

Abstract The invention relates to a device for conducting electrochemical measurements in glass or salt melts, comprising at least one indicator electrode and one reference electrode arrangement, wherein a tip of the indicator electrode intended for immersion in a melt is constructed of a noble metal and said tip being melted gas-tight into a quartz glass tube, and wherein the indicator electrode is passed through the quartz glass tube.
Full Text

Device for Conducting Electrochemical Measurements Background of the Invention
The invention concerns a device for conducting electrochemical measurements in glass or salt melts with a least one indicator electrode and one reference electrode arrangement.
Such devices are widely known, especially from GB 2 057 695. Here, a measurement of the oxygen partial pressure takes place by means of an electrochemical measuring cell, also called the reference electrode arrangement, which is connected with a counter electrode (indicator electrode) through a typical indicator and/or evaluating facility (measuring system). A platinum wire is used as the indicator electrode which is passed through an aluminum oxide body. The platinum wire is freely exposed at the tip of the aluminum oxide body so, that it can come into contact with the melt as soon as the counter electrode dips into this. The aluminum oxide body is mounted in an aluminum oxide tube. In practice, it has become apparent that it is not possible to create a gas-tight lead-through between the platinum electrode and the aluminum oxide body. In this way, oxygen from the atmosphere above the melt, penetrates to the part of the indicator electrode which stands in contact with the melt, so that the values measured there do not correspond to the actual conditions within the melt, and the measurement is thereby erroneous.
Similar measurement arrangements are known for example, from DE 38 11 915 Al. Here too, the indicator electrode is made of platinum.

The determination of iron, sulfur or chromium in glass melts by voltametric analysis with three electrodes is known, for example, from Glastech. Ber. Glass Sci. Techno!. 68(9), pages 273-277 (1995). Even here, the problems mentioned occur. Thus, for example, the size of the electrode surface in the glass must be known exactly.
BRIEF SUMMARY OF THE INVENTION Proceeding from the known prior art devices, an object of the present invention is to improve the measuring accuracy of, for example, oxygen partial pressure measurements in glass or salt melts.
In accordance with the invention, the object is accomplished by the tip of the indicator electrode designed to be immersed in the melts being made of a noble metal and being melted in gas-tight into one end of a quartz glass tube, whereby the indicator electrode is passed through the quartz glass tube (out of the melt into the evaluation facility). A gas-tight mounting means that no oxygen penetrates through the quartz glass tube from outside into the melt to be measured in such an amount as to influence the measurement. Expediently, the noble metal is a metal of the iridium, platinum, palladium or rhodium group or an alloy of at least one of these metals with at least one further noble metal (possibly also from this group). It is conceivable to use the device primarily for short-term measurements.
It is expedient for the connection between the indicator electrode and quartz glass tube on the end of the tube destined to be immersed into the melt to be gas-tight. The tube can be open toward the rear, away from the melt. It is also expedient that the tip of the indictor electrode, which is constructed of noble metal, be connected inside the tube with a measuring wire, preferably made of molybdenum, tungsten or a chromium-nickel alloy (for example, cronix). In this way, the length of the noble metal wire used as an electrode can be kept short in order to save on noble metal.

In the event that the measuring wire is constructed of molybdenum or tungsten, it is possible to install a metal strip of molybdenum between the tip of the indicator electrode which is constructed of the noble metal and the measuring wire. The connection between the noble metal and the measuring wire can be melted into the heat-resistant (quartz glass) tube. In particular, a melted-in metal strip of molybdenum assures almost perfect gas tightness.
A chromium-nickel wire cannot be melted into the quartz glass without further ado, since there exists the danger that the tube will melt at the necessary • temperature. The connection should therefore be arranged preferably behind the melting-in point in the quartz glass tube.
It is advantageous for a high measuring accuracy that a reference electrode be arranged in a solid electrolyte capillary tube closed on one end, which is mounted in a ceramic tube with its end facing away from the closed end through which the reference electrode is passed. It is also advantageous that the end of the reference electrode in the solid electrolyte capillary tube be surrounded by a reference material which is made of a metal-metal oxide, preferably a nickel-nickel-oxide powder mixture. The reference electrode itself is suitably constructed of a chromium-nickel alloy.
It is furthermore expedient that the quartz glass tube and the ceramic tube be filled with corundum. Furthermore, it is advantageous that the quartz glass tube and the ceramic tube be mounted in a common carrier tube, which is preferably constructed of ceramic and which has a connection piece of usual type at its end facing away from the immersion end for mechanical coupling and for connecting indicator electrode and reference electrode with a measurement system. The carrier tube can be made of aluminum oxide and be filled with spherical corundum.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
The foregoing summary, as well as the following detailed description of preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention,

there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings:
Figure 1 shows a representation of the device of the invention;
Figure 2 is a longitudinal section through the device of the invention;
Figure 3 is a longitudinal section through the indicator electrode melted into the quartz glass tube; and
Figure 4 is a section through a device with three electrodes.
DETAILED DESCRIPTION OF THE INVENTION The device represented in Figure 1 has a carrier tube 1 which is constructed of aluminum oxide. A connecting piece 2 is arranged, on the carrier tube 1 on its end facing away from the immersion end, which is inserted into a holder (not shown in the Figure), for example a metal lance. The wires passed through the carrier tube 1, the measuring wire 3 and the reference electrode 4 are connected through connecting piece 2 with a measuring system, that means with a usual indicator and/or evaluating unit. Within the carrier tube 1, the measuring wire 3 and the reference electrode 4 are passed through quartz glass capillary tubes 5 and imbedded in ball corundum 6.
At the end of the device facing toward the immersion end of the carrier tube 1, the reference electrode arrangement 7 and the quartz glass tube 8 are situated. The reference electrode arrangement 7 has a ceramic tube 9 of aluminum oxide through which the reference electrode 4 is passed up to the solid electrolyte capillary tube 10. The solid electrolyte capillary tube 10 of zirconium oxide has in its interior, as reference material, a nickel-nickel oxide powder mixture, in which the reference electrode 4, which is constructed of a chromium-nickel alloy (cronix), is moimted. The indicator electrode with the measuring wire 3 is passed through the quartz glass tube 8. The tip 11 of the indicator measuring electrode is made of iridium wire. It can, however, also be constructed of platinum, palladium, rhodium or an alloy which

predominantly contains iridium or other metals of the aforementioned group in addition to this other noble metal. The tip 11 of iridium projects into the quartz glass tube 8. The tip 11 is melted in gas-tight into the end 12 of the quartz glass tube 8 along a length of about 2 cm. After this, the material of the indicator electrode changes. In order to save on relatively expensive iridium wire, the remainder of the indicator electrode is a measuring wire 3 made of cronix (chromium-nickel alloy). Instead of cronix, molybdenum or tungsten, for example, can also be used as measuring wire 3.
A further possibility of constructing the indicator electrode is represented in Figure 3. Here, the tip 11 of iridium within the quartz glass tube 8 is connected with a molybdenum strip 13, which is connected at its other end with the measuring wire 3. The measuring wire 3 can in this case, for example, be constructed of molybdenum or tungsten. The molybdenum strip 13 is, in the example depicted, completely melted into the end 12 of the quartz glass tube 8. In this way, a perfect gas tightness can be attained.
Not represented in the Figures is the possibility of leading the molybdenum strip 13 out of the melted-closed end 12 of the quartz glass tube 8 and first connecting it with the measuring wire 3 in the open tube. In such case, cronix would also be possible as measuring wire 3.
The quartz glass tube 8 and ceramic tube 9 are provided with a corundum packing which stabilizes the position of the wires within the tubes.
The device represented in Figure 4 is suited for voltametric measurement, for example, of the iron, sulfur or chromium content in a glass melt. The procedure for this is described, for example, in Glastech Ber. Glass Sci. Technol. 68(9) pages 273-277 (1995). In the carrier tube 1 of aluminum oxide, an indicator electrode and a reference electrode 4 are arranged. The tip 11 of the indicator electrode is constructed of iridium and melted into a quartz glass tube 8. The reference electrode 4 of platinum is arranged in a ceramic tube 9, and a counter electrode 14 of platinum is arranged on the immersion end of the carrier tube 1.

Measurement with the device described enables very reliable results, first and foremost in short-term operation. Since the device can be manufactured very economically, construction as a disposable (one use) probe is possible.
It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.



We claim:
1. A device for conducting electrochemical measurements in glass or salt melts, comprising at least one indicator electrode and one reference electrode arrangement, wherein a tip (11) of the indicator electrode intended for immersion in a melt is constructed of a noble metal and is melted gas-tight into a quartz glass tube (8), and wherein the indicator electrode is passed through the quartz glass tube (8).
2. The device according to claim 1, wherein the noble metal is a metal selected from the group consisting of iridium, platinum, palladium, rhodium and and an alloy of at least one of these metals with at least one further noble metal.
3. The device according to claim 1, wherein the connection between indicator electrode and quartz glass tube (8) at an end (12) of the quartz glass tube (8) intended for immersion into the melt is melted in.
4. The device according to claim 1, wherein the tip (11) is connected with a measuring wire (3) within the quartz glass tube (8).
5. The device according to claim 4, wherein a metal strip (13) of molybdenum is arranged between the tip (11) and the measuring wire (3)
6. The device according to claim 5, wherein the measuring wire (3) is made of molybdenum or tungsten.
7. The device according to claim 4, wherein the connection between the tip (11) and measuring wire (3) is melted into the quartz glass tube (8).
8. The device according to claim 4, wherein the measuring wire (3) is made of a chromium-nickel alloy.
9. The device according to claim 1, wherein the reference electrode arrangement comprises a reference electrode (4) arranged in a solid electrolyte capillary tube closed on one end, the capillary tube on its end opposite the closed end being mounted in a ceramic tube (9), through which the reference electrode (4) is passed, and wherein an end of the reference electrode (4) is surrounded in the solid electrolyte

capillary tube (10) by a reference material which comprises a metal-metal oxide powder mixture.
10. The device according to claim 9, wherein the reference electrode (4) is made of a chromium-nickel alloy.
11. The device according to claim 9, wherein the quartz glass tube (8) and the ceramic tube (9) are packed with corundum.
12. The device according to claim 9, wherein the quartz glass tube
(8) and the ceramic tube (9) are mounted in a common carrier tube (1), having on its
end facing away from the immersion tip a connecting piece (2) for mechanical coupling
and for connecting the indicator electrode and the reference electrode (4) with a
measuring system.
13. The device according to claim 12, wherein the carrier tube (1) is
made of aluminum oxide and wherein it is filled with ball corundum.
14. The device according to claim 12, wherein the carrier tube (1) is made of ceramic.
15. The device according to claim 9, wherein the metal-metal oxide powder mixture comprises nickel-nickel oxide powder.
16. A device for conducting eleotrochemical measurements in glass or salt melts substantially as herein described with reference to the accompanying drawings.


Documents:

1116-mas-1997-abstract.pdf

1116-mas-1997-claims duplicate.pdf

1116-mas-1997-claims original.pdf

1116-mas-1997-correspondence others.pdf

1116-mas-1997-correspondence po.pdf

1116-mas-1997-description complete duplicate.pdf

1116-mas-1997-description complete original.pdf

1116-mas-1997-drawings.pdf

1116-mas-1997-form 1.pdf

1116-mas-1997-form 26.pdf

1116-mas-1997-form 3.pdf

1116-mas-1997-form 4.pdf


Patent Number 208074
Indian Patent Application Number 1116/MAS/1997
PG Journal Number 27/2007
Publication Date 06-Jul-2007
Grant Date 09-Jul-2007
Date of Filing 27-May-1997
Name of Patentee HERAEUS SENSOR-NITE INTERNATIONAL N.V
Applicant Address 1105, B-3530 HOUTHALEN.
Inventors:
# Inventor's Name Inventor's Address
1 DR.JACQUES JOSEF PLESSERS 1105, B-3530 HOUTHALEN.
PCT International Classification Number G01N27/411
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 196 23 687.8 1996-06-14 Germany