JPS60195445A - Ph measuring electrode - Google Patents

Abstract

PURPOSE:To improve the hydrofluoric acid resistance of a pH measuring electrode having an inside electrode, inside liquid and pH responding film by forming a thin film consisting mainly of oxide of iridium or palladium on the surface of a substrate. CONSTITUTION:An inside cylinder 2 consisting of glass and an inside electrode 3 which has a platinum lead wire 4 and is welded with a silver wire fixed silver chloride to a platinum wire are provided into a supporting tube 1 consisting of a resin, etc. and a response film 6 is fixed to the peripheral part 1a of the aperture in the bottom of a supporting tube 1 by an adhesive material 7 so as to seal the aperture. A packing 8 is provided if necessary and an inside liquid which is, for example, an aq. potassium chloride soln. is put into the tube 1. The film 6 is constituted by forming thin films 6b, 6c having excellent hydrofluoric acid resistance and consisting mainly of the oxide of iridium or palladium on both surfaces of a substrate 6a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a measuring electrode, and more particularly to a measuring electrode equipped with a novel and useful response membrane.

[Prior art and its drawbacks]

Conventionally, glass has been used for the response membrane of the measurement electrode (hereinafter referred to as measurement electrode). However, since glass is easily corroded by hydrofluoric acid (HF, hereinafter referred to as hydrofluoric acid) and has a high resistance value, it is difficult to use ordinary adhesives when sealing the response membrane at the end of the measurement electrode. Since this is not possible and must be done using a glass sealing method,
It was necessary to pay close attention to the insulation near the response membrane.

[Purpose of the invention]

Therefore, as a result of various studies in order to eliminate the drawbacks of the above-mentioned conventional techniques, the present inventors focused on the fact that thin films made of iridium oxide and palladium oxide, which are chemically stable and are not affected by acids (including hydrofluoric acid), respond to conditions. However, the present invention has been completed with a configuration that can be immediately applied to conventional rice meters.1.The present invention provides a measuring electrode that is chemically and mechanically stable, has excellent hydroacid resistance, and is easy to manufacture. It is an object.

[Structure of the invention] In a state measurement electrode having an inner electrode, an internal liquid, and a response membrane,
It is characterized in that a thin film mainly made of iridium or palladium oxide is formed on the surface of a substrate as a response film.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is an enlarged view of the main parts of the measuring electrode according to the present invention, where 1 is a support tube made of resin or the like, and 2 is an inner cylinder made of glass. Reference numeral 3 designates an internal electrode, for example, a silver wire to which silver chloride is adhered is welded to a platinum wire, and 4 represents a lead wire made of platinum. Reference numeral 5 denotes an internal liquid, such as an aqueous potassium chloride solution, and the configuration up to this point is no different from conventional measuring electrodes of this type.

Reference numeral 6 denotes a response membrane provided to seal the bottom opening of the support tube 1, and is fixed to the opening peripheral end 1a with an adhesive 7. Note that 8 is a gasket provided as necessary.

The response membrane 6 of this embodiment is different from conventional ones made of glass, and is made of mainly iridium or palladium oxide, which has excellent hydrofluoric acid resistance, on both sides of the substrate 6a (indicated by A and B in the figure). Thin films 6b and 6C are formed. That is, the thin film 61) is applied to both the surface A of the substrate 6a that is in contact with the internal liquid 5 and the surface B that is in contact with the test liquid that is the target of concentration measurement.
+60 is formed.

The responding substances include (1) iridium oxide (Ir0), (2) palladium oxide (PdO), and (3) alloys of iridium and noble metals such as gold (Au), platinum (Pt), and palladium (Pd). Oxides (containing 10% or more of iridium) (4) Oxides (containing 10% or more of palladium) of alloys of palladium and noble metals such as gold, platinum, and iridium.

Next, for an oxide of iridium (Ir), for example, iridium oxide (IrO2X), the manufacturing method and structure of the response film 6 will be described.

First, when the substrate 6a is made of a conductive material such as metal,
As shown in FIG. 2(a), the substrate (1 to 211 tM) 6
Thin films 5b and 5c made of iridium oxide are formed on both sides of a by reactive sputtering or the like. At this time, the thin film 6
The film thicknesses of b, (, and c are preferably 1,000 to 3,000. Then, the thin film 6b l 60 formed on the substrate 6a is cut, punched, or ultrasonic-processed to form the thin film shown in FIG. 2 (b).
) Shape it into a pellet of predetermined dimensions as shown in ().

The metals for the above substrate include platinum (Pt), chromium (
A material with good adhesion to iridium oxide, such as Cr) or tantalum (Ta), is selected.

The substrate 6a is not necessarily made of a conductive material, but may be made of a non-conductive material such as sapphire alumina, glass, or the like. In this case, as shown in FIG. 3, for example, a conductive path 6d is formed on the side of the substrate 6a so that the thin films 51) and 6Q on both sides have the same potential. or,
As shown in FIG. 4, a metal film 6θ may be applied to a substrate 6a, and pressure may be applied to form a thin film 6b+6C on the outside thereof.

Further, the response membrane 6 is not limited to a flat plate shape, but may have a cross-sectional shape that is upwardly shaped, as shown in FIG. 5, in consideration of mounting on the support tube 1.

Note that another method for forming the thin film 61) l60 on both sides of the substrate 6a is to oxidize both sides of an iridium thin plate by thermal oxidation, anodic oxidation, etc. to form a predetermined thin film 6b16.
K may be used to obtain C. In the above embodiments, the response film is formed on both sides of the substrate, but as shown in FIG. 6, the response film can be formed only on one side of the substrate. Components in the figure that are the same as those in FIG. 1 are designated by the same numbers. Here, 6d is a substrate and 6θ is a response film.

Further, FIG. 7 shows a case in which a response film is formed on the entire surface of a wire-shaped substrate.

Components in the figure that are the same as those in FIG. 1 are designated by the same numbers. Here, the bi is the substrate, and the plane is the response membrane formed on the surface of the substrate.
indicates a packing or adhesive for sealing.

In addition to the above-described method for producing a responsive membrane, there is also a method in which a thin film of iridium, palladium, or the like is formed on a substrate by sputtering or vapor deposition, and then subjected to oxidation treatment.

This oxidation treatment method can be improved a few times: (Immersion in 11 IN of KOH or NaOH and heat treatment at a temperature of 700 to 1000° C. in an oxygen or oxidizing atmosphere.

(2) K(l(and KNO,
400-500°C).

(3) Treat in an oxidizing flame of 800-9000C.

and so on.

(Effects of the Invention) In the measurement electrode according to the present invention, a thin film made of iridium or palladium oxide is formed on the surface of the substrate and is used as a response membrane. Even if the U-1 concentration is measured by immersing the electrode, the response membrane will not be corroded by the test liquid, and a chemically and mechanically stable measurement electrode can be obtained, as well as requiring strict sealing work. In addition, the response membrane can be attached to the opening of the support tube with adhesive, etc., without the need for high insulation. There is no problem, and its production is extremely simple.

Further, the excess bias generated during the measurement of the concentration is offset by the thin films on both sides, and drift components such as temperature drift of the response membrane itself are also suppressed by the thin films, so that measurement accuracy is improved.

Furthermore, the measurement electrode of the present invention can be used by being connected to a conventionally widely used field meter as is by making the structure other than the response membrane similar to that of a conventional glass electrode.

Note that it is also possible to integrally incorporate a comparison electrode (or even a temperature compensation electrode) into the measurement electrode according to the present invention to form a composite electrode.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a main part of a field measuring electrode according to the present invention, and a cross-sectional view showing an embodiment. 6...Response membrane, 6a...Substrate, 6b, 6C...Thin film. Fig. 2 6C Fig. 3 Special opening JGO-195445 (4) Fig. 6 Fig. 7 Fig. 5 Convex

Claims (1)

[Claims] A measurement electrode trap having an inner electrode, an internal solution, and a response membrane is placed,
A state measurement electrode characterized in that a response film is a thin film mainly made of iridium or palladium oxide formed on the surface of a substrate.