JPS5829869B2 - Reference electrode for high temperature and high pressure aqueous solutions - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reference electrode for high-temperature, high-pressure aqueous solutions in which the entire reference electrode is disposed in a measurement object and is used at the same temperature and pressure as the measurement object. If the container has a structure in which there is no communication between the inside and outside of the container, the potential of the reference electrode does not deviate from the unique temperature-dependent value due to temperature rises, and the reaction electrode portion deteriorates due to long-term use, The present invention relates to a reference electrode for high-temperature, high-pressure aqueous solutions, in which a deteriorated reaction electrode part can be replaced while the reference electrode is fixed to the lid of a pressure vessel.

In general, the reference electrode is a reaction consisting of a metal and a sparingly soluble salt or oxide of the metal formed on the metal surface, such as the AglAgCIKC7 aqueous solution 1 liquid junction or the HglHg01KOR aqueous solution 1 liquid junction. an electrode portion, an aqueous solution of an electrolyte containing a common anion for the sparingly soluble salt or an electrolyte that is a readily soluble hydroxide for the sparingly soluble oxide, a container for isolating the aqueous electrolyte solution from the measurement target; It consists of a liquid junction.

Reference electrodes for high-temperature, high-pressure aqueous solutions are subject to moderate structural and measurement limitations due to the harsh operating environment of high temperature and high pressure.

In order to avoid this restriction, the main body of the reference electrode is placed in a mild environment of low temperature and low pressure or low temperature and high pressure, and only the liquid junction is communicated with the measurement target under high temperature and high pressure. Reference electrodes are known.

However, the voltage measured by the reference electrode of the external electrode method includes errors due to other potential differences such as temperature and pressure differences between the environment where the reference electrode body is placed and the measurement target. In measurements of relative changes in the electrode potential of a measurement target due to pressure changes or pressure changes, there is a drawback that the range of use is significantly limited.

Like the reference electrode of the present invention, the entire illumination electrode is placed in the measurement object and used at the same temperature and pressure as the measurement object (
The reference electrode of the "internal electrode method" (hereinafter referred to as "internal electrode method") does not have such a drawback.

Currently, internal electrode type and external electrode type reference electrodes for high-temperature, high-pressure aqueous solutions are each used depending on the purpose.

For reference electrodes for high-temperature, high-pressure aqueous solutions using internal electrodes,
As the reaction electrode part, the above-mentioned Ag l AgC7 is used.

In addition to Hg l HgO, others are Ag lAgBr,
AglAgI.

Ag l AgO= P t l P to 2 , I
r l I ro 2 , Rhl Rh2o3. Z
r 1Zr02. Ag lAg25o4. Hg lHg
2804. Pb l PbSO4゜I-(gIHg2
There are C12 and the like, each of which constitutes a reference electrode in combination with an appropriate electrolyte aqueous solution.

As the liquid junction, a salt bridge or a porous sintered body, such as a zirconia sintered plug, an asbestos twine, a porous synthetic resin, a filter paper press molded product, etc., are used.

The inside of the container communicates with the external solution to be measured via a liquid junction, and is not completely sealed.

Therefore, during measurement, an interface or a diffusion layer between the aqueous electrolyte solution and the solution to be measured is formed within the liquid junction.

Conventional internal electrode type reference electrodes for high-temperature, high-pressure aqueous solutions have a short lifespan, and the first reason for this is the reference electrode caused by changes in the concentration of the electrolyte aqueous solution due to the outflow of the electrolyte aqueous solution in the container or the inflow of the external aqueous solution to be measured. An example of this is fluctuations in the potential of the electrodes.

In other words, in a reference electrode that has a structure in which there is no communication between the inside and outside of the container except at the liquid junction, due to the difference in thermal expansion coefficient between the material making up the container and the electrolyte aqueous solution inside, thermal expansion at the liquid junction or Liquid enters and exits through the damaged portion of the container caused by the difference in coefficients.

Usually, the coefficient of thermal expansion of the electrolyte aqueous solution is larger than that of the constituent material of the container, so when the temperature rises, the electrolyte aqueous solution flows out, and when the temperature falls, the external solution to be measured occurs.

For this reason, in the past, a gas phase was provided inside the container only when the external solution to be measured coexisted with the gas phase.
A reference electrode was used that had a structure that communicated the gas phase inside and outside the container.

However, a reference electrode of this construction cannot of course be used if the external solution does not coexist with the gas phase.

A second reason for the short life of conventional thermal electrodes is deterioration due to alteration or detachment of poorly soluble metal salts or oxides of the reaction electrode.

However, because of the integrated structure of conventional internal electrode type reference electrodes, it was not possible to replace deteriorated parts, and the only option was to discard the entire reference electrode.

The purpose of the present invention is to eliminate the drawbacks of the conventional internal electrode type reference electrode, and to eliminate the outflow and inflow of the aqueous solution when the temperature rises and falls due to the difference in thermal expansion coefficient between the container constituent material and the internal electrolyte aqueous solution. Instead, it is an object of the present invention to provide a reference electrode for a high-temperature, high-pressure aqueous solution in which the potential of the reference electrode exhibits a unique value dependent on temperature.

Another object of the present invention is to configure the reference electrode in such a way that the reaction electrode can be replaced when the poorly soluble metal salt or poorly soluble metal oxide in the reaction electrode deteriorates, so that it can be used continuously. The object of the present invention is to provide a reference electrode for high-temperature, high-pressure aqueous solutions that can perform

To explain the content of the present invention in more detail, the reference electrode of the present invention has a structure in which there is no communication between the inside and outside of the container at locations other than the liquid junction, has a small coefficient of thermal expansion, and has a chemical resistance to the electrode constituent materials. It is characterized in that an inert substance such as zirconia powder, high-purity α-alumina, etc. is present as a spacer together with the aqueous electrolyte solution in the container, and at the same time, a pressure regulator is provided in a part of the container.

As the pressure regulator in the present invention, one having a deformable diaphragm, for example, a diaphragm type pressure regulator, a bellows type pressure regulator, etc. is suitable.

The appropriate amount of spacer material to be placed in the container is determined as follows.

The body expansion coefficients of the electrolyte aqueous solution, the metal of the reaction electrode part in the container, the poorly soluble metal salt or hardly soluble metal oxide of the reaction electrolyte part, the constituent material of the container, and the substance used as a spacer are αsob, αm, αS.

Let αcon and αsp be the volume or volume at temperature T1 when creating the reference electrode, respectively, Vso6°Vm
, V s , Vcon (volume of container), V s
Let it be p.

Further, the temperature at which the reference electrode is used is assumed to be T2. now,
If Vcon, Vm + Vs, and T1 are fixed values, and T2 is a variable, then at temperature T2, the amount of the liquid/spacer mixture in the container that protrudes from the container in order to inflate the pressure regulator is expressed as (V): The following formula (
1) holds true.

If the temperature range in which you want to use the electrode is T1≦T≦T2maxmax (T2 is the upper limit of the temperature in which the reference electrode is used), then if T2-T1-JTmax, then JT is O≦J
It can take the range T≦J Tmax.

AV where the pressure regulator does not cause damage such as cracking or damage.
When the maximum allowable amount is lψmaX and the minimum allowable amount is [stock], 3A Vomin (including the case where it becomes a negative value), then in JT where 0≦, (T≦J Tmax, A
Maximum value of V 11 Vmax and minimum value JVmin are
Regarding the above A Vomax, J Vomin 1
,j V max≦A■0maxA■0m1n≦JVm
If it is in, the pressure regulator will not be damaged.

If Vsp holds formulas (5) and (6), then O≦JT≦
, d T max, JV0min≦JVmin≦JV≦JVmax≦JV0
max and the pressure regulator will not be damaged.

Also, from equation (2), V con −Vm−V s −
V sp= V sob > 0 therefore ■con−■m−
■s〉Vsp...(7) After all, (5), (6)
, (7), when O≦, (T≦, j T max, V sp must be selected within the range of the following equation (8).

Although the temperature varies depending on the substance used as a spacer and the type of container construction material, if the reference electrode is used below a certain temperature, it can be used without a pressure regulator.
Although it is possible to prevent the outflow and inflow of liquid with only a spacer, it is generally difficult to prevent this with only a spacer when used at a high temperature exceeding the above temperature.

For example, in the case of the silver-silver chloride reference electrode according to the example described below, it was possible to prevent liquid outflow and inflow only with the zirconia powder spacer at temperatures below about 200°C; At temperatures exceeding ℃, it was not possible to prevent this by using a spacer alone.

In other words, when used at such high temperatures, the range in which the temperature rises and falls is large, so the temperature dependence of the coefficient of thermal expansion of the material used to construct the container and the material used as the spacer cannot be ignored. A. This is thought to be because it would be difficult to prevent liquid from flowing out or flowing in throughout the entire process.

The following is a study on the case where no pressure regulator is provided.

(a) When the temperature dependence of the thermal expansion coefficient α can be ignored.

1 It is necessary to select a Vsp that satisfies -0 on the right side of (4) when 0≦JT≦lTmax.

Its value is.

However, it can only be used in a relatively narrow temperature range where the temperature dependence of α can be ignored.

(b) When the temperature dependence of the coefficient of thermal expansion α cannot be ignored.

It can be assumed that the concentration of the liquid in the container does not change☆☆ Let the allowable value of AV be A V max.

When α is Taylor expanded with respect to AT, α(JT)=
, Σαi, (T i +=0, but now α(JT)=−α.

+α, JT, the formula ■ for a specific Vsp value is
(When solving for T, if JTA≦JT≦JTB, then JT > AT B cannot be controlled with just a spacer and requires a pressure regulator.

In both cases (a) and (b), the conditions for using a reference electrode are severely restricted, and the operating temperature range is considerably limited.

However, the reference electrode of the present invention has a pressure regulator in a part of the container and at the same time has an appropriate amount of spacer material represented by the above formula (8) in the container, so that the reference electrode can be used at high temperatures. However, even if the temperature rises and falls over a wide range, no outflow or inflow of liquid occurs.

Therefore, compared to a reference electrode that includes only either a spacer or a pressure regulator, it can be stably used over a wide temperature range.

Furthermore, since the reference electrode of the present invention has a structure in which the inside and outside of the container are not communicated except at the liquid junction, it can be used whether or not the external solution to be measured coexists with the gas phase. can.

Further, the reference electrode according to the present invention is configured so that it can be replaced when the reaction electrode portion deteriorates.

This point will be explained with reference to FIG. 1, which is a cross-sectional view of a silver-silver chloride reference electrode in which silver and silver chloride are used as reaction electrode parts, which is an embodiment of the present invention.

The container consists of a container body 1, an upper lid 2, and a lower lid 3 which are removably joined by screwing, fitting, etc., and an electrolyte aqueous solution (0.01 NK (1 aqueous solution) 4 is contained in the container). ing.

These parts 1, 2.3 constituting the container are made of polytetrafluoroethylene (hereinafter referred to as PTFE) resin filled with zirconium oxide as a filler, which has excellent mechanical strength and electrical insulation, and is chemically inert. Made of materials.

The joints are sealed with a thin film made of PTFE.

The silver frame 5 is covered with a PTFE tube or the like, is inserted into the container through the upper lid 2, and is fitted with a nut 6.
Fixed by

At the tip of the silver frame 5, by a method such as electrolysis or melting,
A silver-silver chloride electrode 7, which is a reaction electrode portion in which silver chloride is adhered to the surface of metallic silver, is connected by a detachable method such as screwing or fitting.

Therefore, even if this silver-silver chloride electrode γ deteriorates, the container can be dismantled and the deteriorated silver-silver chloride electrode 7 can be replaced.

In addition, with this configuration, even if the concentration of the electrolyte aqueous solution fluctuates due to an abnormal temperature rise or the passage of a large current, or the electrolyte aqueous solution is contaminated by an inflow of solution from the outside, the electrolyte aqueous solution can be replaced. be.

In this way, the potential of the reference electrode does not deviate from the unique temperature-dependent value even when the temperature rises and falls during use, and even if the reaction electrode body deteriorates, it can be replaced, so the life of the reference electrode of the present invention is extended. can be said to be semi-permanent.

Example 1 A reference electrode for high-temperature, high-pressure aqueous solutions according to the present invention as shown in FIG. 1 was prepared.

A container body 1, an upper lid 2, and a lower lid 3 made of PTFE resin filled with zirconium oxide as a filler were screwed together after wrapping a PTFE thin film tape around their joints to form a container.

A silver frame 5 covered with a heat-shrinkable PTFE tube was inserted into the container through the upper lid 2 and fixed to the upper lid 2 with nuts 6.

A silver-silver chloride electrode 7, in which silver chloride was melted and adhered to the surface of metallic silver, was screwed onto the tip of the silver frame 5.

The lower lid 3 is made of heat-shrinkable PTF with a zirconia sintered plug.
A liquid junction 8 covered with an E-made tube was fixed with a nut 9.

A diaphragm pressure regulator 10 was joined to a part of the container body 1 via a PTFE thin film seal.

At this time, the container capacity was 4.3 ml. Inside the container are 119.89 zirconia powder and 0.0 zirconia powder as spacers.
41.6 rnl of IN potassium chloride aqueous solution was sealed.

Test Example 1 The reference electrode of the present invention manufactured in Example 1 and the conventional silver-silver chloride type reference electrode (Comparative Example 1) having the same configuration as Example 1 except that no spacer and pressure regulator were provided. ) was immersed in pure water and the temperature was raised and lowered repeatedly.

The potential of the reference electrode at room temperature before and after such treatment was measured in comparison with a saturated Amagi electrode.

It can be seen that the electrode of the present invention does not easily change the concentration of the electrolyte aqueous solution inside the container as the temperature rises and falls, and has a stable potential.

Test Example 2 A reference electrode of the present invention that is the same as the reference electrode of the present invention in that it has zirconia powder as a spacer in the container, but does not have a pressure regulator (Comparative Example 2), and a reference electrode of the present invention according to Example 1 The electrodes were subjected to the same treatment as in Test Example 1 and tested.

The configuration and specifications of Comparative Example 2 are the same as the reference electrode of Example 1, except that a pressure regulator is not provided.

The reference electrode for high-temperature, high-pressure aqueous solutions according to the present invention is less likely to change the concentration of the electrolyte aqueous solution inside the container due to temperature rise and fall than a reference electrode that has a spacer inside the container but does not have a pressure regulator, and can maintain a stable potential. It turns out that it has.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a reference electrode for high-temperature, high-pressure aqueous solution according to an embodiment of the present invention. 1...Container body, 2...Top lid, 3.
... lower lid, 4 ... 0.0 IN potassium chloride aqueous solution, 5 ... silver frame, 6 ... nut, 7 ... silver - Silver chloride electrode part, 8...
... Zirconia sintered plug, 9 ... Nut, 1
0...Diaphragm pressure regulator, 11...
...zirconia powder, 12...conutx...
Type seal, 13... Lid of the container containing the solution to be measured at high temperature and high pressure.

Claims (1)

[Scope of Claims] 1. A metal rod, a reaction electrode portion located at the tip of the metal rod and made of a metal and a sparingly soluble salt or oxide of the metal formed on the metal surface; A reference electrode for a high-temperature, high-pressure aqueous solution consisting of an electrolyte or easily soluble hydroxide aqueous solution containing a poorly soluble salt and a common anion, a container for isolating the electrolyte aqueous solution from a solution to be measured, and a welded part, in which a spacer substance is used. A reference electrode for a high-temperature, high-pressure aqueous solution, characterized in that it is dispersed in the electrolyte aqueous solution and exists in a container, and a pressure regulator is provided in a part of the container. 2. A high-temperature, high-pressure device according to claim 1, wherein the reaction electrode portion is removably joined to the tip of a metal rod, and the container has an upper lid and a lower lid removably joined to the container body. Reference electrode for aqueous solutions. 3. The reference electrode for a high-temperature, high-pressure aqueous solution according to claim 1, wherein the spacer material is zirconia powder and the pressure regulator is a pressure regulator consisting of a deformable diaphragm.