Capillary reference half-cell

Details Capillary reference half-cell Capillary reference half-cell

1994-08-12

1996-02-13

Bell, Bruce F.

Electrolysis: processes, compositions used therein, and methods

Electrolytic analysis or testing

For corrosion

204435, 2057945, G01N 2726

Patent

active

054909163

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The present invention relates generally to a method and apparatus for providing a reference half-cell or more specifically to a capillary type reference half-cell having a liquid reference solution constrained from free flow volume discharge.


BACKGROUND OF THE INVENTION

Investigation of the chemistry of natural waters including but not limited to underground aquifers, and above ground lakes is usually accomplished by taking water samples and analyzing the samples in a laboratory. Many chemical species are detected and measured for various purposes. For example, waste water discharge may be monitored for the presence of hazardous chemicals including but not limited to inorganic cations and anions, for example, sulfur compounds and metal compounds, and organic compounds. Another application is the detection and quantification of chemical tracers which are used for determining flow patterns. Chemical tracers include but are not limited to bromides, chlorides, sulfides, and pH. In addition, chemical analyses are routinely performed for chemical process flow stream monitoring of processes including but not limited to winemaking, electroplating, hydrometallurgy, papermaking, chemical manufacture, and many other industrial processes.
Analysis for determining the presence and amount of particular chemical species may be carried out using an electrochemical cell wherein the voltage potential is related to a difference in chemical concentration between a known reference solution and the unknown sample test solution. The classic electrochemical cell is two beakers having solutions of differing concentrations or compositions with a salt bridge in contact with both solutions and electrodes in each solution which are connected to a voltmeter. The classical electrochemical cell has the attributes of (1) physical isolation of the two solutions, and (2) electrical communication (via a salt bridge) between the two solutions, and is useable in a laboratory setting, but is inconvenient for field applications, especially submerged in-situ measurement applications.
Various methods and devices relying on the physical principles of the classic electrochemical cell have been used in field applications. In field applications, the beakers of the classic cell are replaced with a sensing half-cell and a reference half-cell which are placed in a test solution and connected by a voltmeter. Reference half-cells for field applications have the same two attributes of solution isolation with electrical communication as the classical electrochemical cell. Isolation of the solutions is fundamentally necessary because intermingling of solutions would change the electrochemical potential. Reference half-cells for field applications, grouped according to how solution intermingling is prevented, tend to be of two main types; non-flowing and flowing, wherein the reference solution either flows from the half-cell or it remains within the half-cell.
Electrochemical reference half-cells of the non-flowing type include the liquid filled classical cell and a gel filled submersible cell, for example, a Model 13-620-259 gel-filled calomel reference half-cell, manufactured by Fisher Scientific Company, Pittsburgh, Pa. In gel-filled cells, an amount of reference solution is placed within a vessel and remains within the vessel, hence the solution is non-flowing. In the classic cell, the connection between the non-flowing reference solution and the test solution is a salt bridge, and in the submersible cell, it is a virtually non-porous solid which closes one end of the vessel containing the reference solution. Hence, as in the classical cell, the gel-filled cell reference solution gel is physically prevented from intermingling with test solution yet is in electrical contact through the virtually non-porous solid. The virtually non-porous solid forms an electrical junction. Ideally, it is desirable to minimize the effect of such a junction on the operation of the half-cell. The effect of the junction is minimized by making the virt

REFERENCES:
patent: 2289589 (1942-07-01), Pomeroy
patent: 3455793 (1969-07-01), Watanabe et al.
patent: 3463717 (1969-08-01), Koopman et al.
patent: 3705089 (1972-12-01), Grubb
patent: 4929426 (1990-05-01), Bodai et al.
Hack One Electrode System Manual, 1988 pp. I, 1, 3, 16, 22-26.

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