JPS61225643A - Measurement of concentration of strong acid or strong base in solution with water - Google Patents

Abstract

PURPOSE:To enable automatically continuous measurement, by arranging a metal terminal connected electrically to an electrochemical system extending outside a container as main component while a film electrode adapted to generate a fixed internal potential difference solely depending on the temperature is used between the metal terminal and a film phase. CONSTITUTION:An indicator electrode 2 as film electrode, a reference electrode 3 and a terminal 4 for measuring liquid temperature are immersed into a measuring tank 1, a sample solution is introduced into the tank 1 through an liquid feed tube 5 and drained outside the tank 1 through a drain tube 6. While the sample solution with the unknown concentration is running through the tank 1, the terminal voltages between the electrodes 2 and 3 is passed through an impedance converter 7 and a signal involving the liquid temperature detected with a terminal 4 is converted into a voltage with a signal converter 8. Both are inputted into a concentration computing unit 9. With the computing unit 9, the output signal voltages of the converters 7 and 8 obtained from the sample solution are compared with the reference data separately to measure the concentration corresponding to the sample solution, which is outputted. This enables automatically continuous measurement of the concentration of the sample solution.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to the use of strong acids or strong +1! ! The present invention relates to a method for measuring the concentration of a group, and more specifically, to a method capable of continuously and automatically measuring the concentration of a particularly high concentration of a strong acid or strong base with high precision by potentiometric measurement.

[Technical background of the invention and its problems] In the fields of electrolysis industry, plating industry, pickling of metal products, reprocessing of spent nuclear fuel, metal wet smelting, or metal sample dissolution treatment for wet analysis. is an elemental technology that requires the measurement of the concentration of strong acids such as hydrochloric acid, sulfuric acid, and nitric acid, or strong bases such as sodium hydroxide, potassium hydroxide, and calcium hydroxide, dissolved in water at high concentrations. In these industrial fields, unmanned operation through automatic control is progressing, and therefore there is a strong demand for a method for continuously and automatically carrying out such concentration measurements.

Conventionally known methods for measuring concentration include (1) a method of determining from electrical conductivity, (2) a method of determining from v, degrees, and (3) a method of determining from absorbance. However, these methods are subject to measurement limitations due to the type of strong acid or strong base being measured, and the presence of air bubbles in the sample solution may cause measurement values to fluctuate, which hinder continuous automation of measurements. Therefore, neither method can be said to be satisfactory.

On the other hand, if it is an aqueous solution in which a strong acid or a strong base is dissolved at a low concentration, the pH should be measured in advance with a pHJ) measuring device using a glass electrode, regardless of the type of acid or burial mound. P) It can be determined from the relationship between I and concentration. Since this method is based on potentiometric measurement, continuous and automatic measurements can be performed without being affected by the generation of bubbles in the sample solution. However, long-term continuous use using glass electrodes)j! p) such that it is measurable
The range of l is 2~! 0 strong acid or strong kJ in the range of 2
One is dissolved in high concentrations outside of this pH range, one is collated to be used with glass electrodes? l! Verification in the liquid path at the pole? Accurate measurement is impossible due to the liquid potential generated between the electrode liquid of the 11 electrodes and the liquid to be measured. Furthermore, even if such a liquid junction potential could be measured separately, in a strongly acidic solution, the measured potential of the glass TrL8ii would change over time during immersion in the sample solution, making it difficult to obtain a constant convergence value. However, this change over time itself has the problem of poor reproducibility.On the other hand, in strongly basic solutions, the potential measurement value of the glass electrode is affected not only by the pH but also by the cation concentration in the sample solution. The problem with 0 and above, which has the problem that the responsiveness of
John Willie and φ Sons, 1964) [RoG, Bates, 7Determi
natian of pH: τheory
andPractice” (JobIllWile7
and 5ons, April 1964, pages 315-322.

[Purpose of issue in January] The present invention solves the conventional problems and enables continuous automatic measurement regardless of the type of strong acid or strong base and without being affected by the generation of bubbles in the sample solution. The object of the present invention is to provide a method for measuring the concentration of a strong acid or strong base in a solution with water, which applies a practical potentiometric measurement method and is capable of measuring high concentrations.

[I of invention! [Summary] In the course of intensive research to achieve the above object, the present inventor discovered the use of Japanese Patent Laid-Open Publication No. 56
-77751 and Needlatch.

Journal Number of Electrochemical Society
, No. 127@, pp. 2122-2130 (1880) ()fiedrach, J. Electro
chem, Sac,, 127, 2122
-2130 (1980)], if a membrane electrode similar to the hydrogen ion senna described in
For an aqueous solution in which a strong acid or strong base is dissolved, the potential of the indicator electrode is not determined only by the pH as described above, but theoretically it depends on the concentration of the strong acid or strong base itself. I got the idea that it should be.

As a result of various studies based on this idea, the inventor of the present invention found that when the above membrane electrode is used,

We have newly discovered that this membrane electrode exhibits excellent potential responsiveness even when measuring the concentration of a solution of a strong acid exceeding 2 mol/cm or a strong base exceeding 1 mol/cm in water, which has not been measured using this membrane electrode. The present invention was completed through these experiments.

That is, 1. A strong acid or a strong a! in solution with water according to the present invention.
The method for measuring the concentration of the group is to immerse an indicator electrode and a reference electrode in a sample solution consisting of a solution containing a strong acid or a strong base, and calculate the sample solution from the voltage generated between the terminals of the indicator electrode and the reference electrode. A method for measuring the concentration of a strong acid or strong base in a container, the indicator electrode comprising a fluid-impermeable membrane made of oxygen ion conductive ceramic;
an electrochemical system in contact with at least a portion of the inner surface of the container; and a metal terminal electrically connected to the electrochemical system and extending to the outside of the container; It is characterized by an 18ITtL pole that generates a constant internal potential difference that depends only on temperature between the two.

In the measurement method of the present invention, first, the target sample solution is a solution with water in which one strong acid or strong base is dissolved. Even if coexisting substances exist,
``Their effects on the activities of hydrogen ions and water in the sample solution can be ignored. Furthermore, as the concentration of a strong acid or strong base increases, the activity of hydrogen ions or the average activity of strong acids, or the activity of hydrogen ions or the average activity of strong bases increases monotonically, and the activity of water increases. is simple y4
solutions of decreasing concentration ranges.

Next, a membrane electrode, which is an indicator electrode used in the method of the present invention, will be described. The inner surface of the container, which contacts at least the electrochemical system, is composed of a fluid-impermeable membrane made of oxygen ion conductive ceramics.

The oxygen ion conductive ceramics include the type of strong acid or strong base in the sample solution;

Various types of these can be used depending on the concentration range, but among them, oxygen ion wheel wheels with high ((1
, close to 0), and it is preferable that dissolution, formation of shinwa, or other specific chemical reactions with the test solution are difficult to proceed.

As such oxygen ion conductive ceramics, stabilized zirconium oxide (Zr02) is used when the sample solution is a strong acid solution, and stabilized zirconium oxide (Zr02) is used when the sample solution is a strong base solution, in addition to the above stabilized zirconium oxide. Thorium oxide (T1102), cerium acetate (Ce02), bismuth oxide (Bi203), lanthanum oxide (C-type L), which has been given oxygen ion conductivity by doping with oxides of
n203), etc. These may be used alone, or a solid solution of two or more types may be used.

On the other hand, in the above-mentioned indicator electrode, the electrochemical system in contact with the inner surface of the container made of the fluid-impermeable membrane made of the above-mentioned oxygen ion conductive ceramics is not particularly limited, but is as follows: The two types described in can be cited as suitable. That is, (1) a combination of an electrolyte aqueous solution with a constant pH and an aqueous solution reference electrode immersed in the electrolyte aqueous solution or the electrode body of the aqueous solution reference electrode that constitutes the aqueous solution reference electrode using the electrolyte aqueous solution as an electrode liquid: 1 usually known as the second branch electrode.

That is, a saturated calomel electrode or a silver-halogenated electrode can be used.

■As a method of constructing a large-capacity electrode together with elemental ion conductive ceramics, a mixture of a metal and an oxide of the metal or a mixture of two types of oxides of a single metal with different valences is used. Combining electronically conductive conductive leads: Suitable mixtures of metals and oxides of the metals include copper--copper meride or mercury-mercury mixtures, and metal atoms of the same metal. As a mixture of two types of oxides with different values, for example,
Examples include mixtures of iron-magnetite and magnetite-hematite (magnetite-hematite K).

In this way, when constructing a large electrode with oxygen ion conductive ceramic as a 1Ml gas chemical system, a mixture of the above metal and an oxide of the metal or a mixture of the same metal is placed in a container made of the oxygen ion conductive ceramic described above. A mixture of two types of oxides having different metal valences is filled, and a conductive lead for electrically connecting the mixture and the above-mentioned metal terminal is buried in the mixture together with the inner wall surface of the container and the Jfi M sacell. It is preferable to have a structure in which the two are in contact with each other.The conductive lead is preferably an inert electronically conductive wire or rod such as a platinum wire or a carbon rod.Furthermore, in this case, the phase of the membrane that is the container Since the potential difference between the mixture and the conductive lead depends on the oxygen partial pressure within the container, it is desirable to provide a sealing member to isolate the inner surface of the container, the mixture, and the conductive lead from the outside air.

The detailed shape and structure of the indicator electrode are not limited in any way as long as it has the basic 4I configuration described above; for example, the electrochemical system is in contact with at least a part of the inner surface of the container. It may extend to the outside of the container as long as it is allowed to do so.

In the membrane electrode that is the indicator electrode used in the method of the present invention,
It is considered that a chemical equilibrium expressed by the following equation (1) is established on the surface of the membrane electrode that comes into contact with the sample solution.

02- (in oxygen ion conductive ceramic membrane) + 2
) 130° (in sample solution): 3H20 (in sample solution) (I) where: Chemical potential 'j of component i: %i.

Electrochemical potential is 7Lis ion valence is zi.

If the internal potential of the phase containing component i is φi, and the Faraday constant is F, then μi + ZiFφ, (II), and from equation (I), 7Lo2− + 27LH30−= ”)120 (m
).

JLO2--2FφQ2-+2CkH30+ +FφH
20)” 3IL)+20 (ff).

On the other hand, if the interfacial potential difference at the surface of the membrane electrode in contact with the sample solution is ΔΦ.

Δφ−φ. 2--φH2o(v) Therefore.

Δφ” (IL02- “”) 130”- Pot H2 (1
)/2F (■), and the activity of component i is expressed as ILi.

PH” −loglo a u3o+ (■)
Therefore, if the standard state is indicated by a shouldered 0, and the gas constant is R1 and the absolute temperature is T, then pi mar + RT log, ai, (Vl)
From Δφ−(gO2−” 2 PH30+−3μ, H2O)
/2F-Katsuya Run,,H-4,o,,au2o (■
) holds true.

Here, in the sample solution, does one strong acid or strong base dissolve alone at a high concentration as described above?

Alternatively, even if there are coexisting substances, the sample solution and the inside of the membrane of the membrane electrode may be different from each other because they are in a solution with water such that their influence on the activity of hydrogen ions and water in the sample solution can be ignored. The internal potential difference Δφ between the pH of the sample solution and the activity of water' R20
Determined depending on.

By the way, it is known that in a dilute solution, the lower the solute concentration, the closer the solution becomes to the ideal solution. Therefore, when the concentration of the strong acid or strong base in the sample solution is low, the activity of the solvent water a ) +20 is approximately - constant; display)
- For example, in sulfuric acid at 25°C, llj
% Chemical Handbook” 2nd edition (edited by the Electrochemical Society, published by Maruzen, 1)
974), page 125, 0.1 mol/kg (f
The same applies to moles/kg below the molar concentration display) and fi
& H20-0, 99B4, at 0.01 mol/kg a H20-0, 1313960.

o,ooos moles/kg! t a H20=0.
It is 99998.

At this time, in equation 1 (IX), Δφ is substantially p)l
It can be seen that it depends only on That is, the membrane electrode used in one method of the present invention has m-ability similar to that of the hydrogen ion sensor described in JP-A-56-77751 mentioned above in a low concentration aqueous solution of a strong acid or strong base.

However, the above-mentioned "Electrochemistry Handbook jp, 125~
According to 12B, at 25°C, the concentration in terms of molarity of sulfuric acid and sodium hydroxide (concentration in terms of volumetric molarity calculated using the density data of aqueous solutions in [vt Gas Chemistry Handbook, p. 130)] (also listed) &
H20 is 3.730 mol/kg (3,25
mole/cross) 0.80. 9.304 mol/kg (
6,36 mol/k), 0o40, sodium hydroxide, 4.7118 mol/k, (4,72 mol/k)
0.80 when 11.54 mol/kg (1
As the concentration of strong acids or bases increases, the activity of water increases, such as 0.40 at 0.8 mol/liter)
gradually decreases, so that the membrane electrode no longer functions as a hydrogen ion sensor. In such a high concentration region, the value of Δφ in formula (IX) depends on the type of strong acid or strong base. This is because the mole fraction of H20 is 11H□, and the activity coefficient on the mole fraction scale is rH20)! 3
If the volumetric molar concentration of 0+ is CH304, and the activity coefficient on the volumetric molar concentration scale is lH3O+, the formula (IX, ) is.

ΔφW(μo2−+ 2JL n30+ −3P H2
0) /2F10RT (log, CH3o+) /F
-3R (loge M12o)/2F + R<rog
e Yu30")/'-3RT(lollefH2(
1)/2F (X) and i! The activity coefficient r is different from that for solutes in dilute solutions.
This is because n2o and lH3O+ depend on the types of solution components.

From equation (X), it can be seen that when the sample solution is an aqueous solution of a strong acid, &H3o+ increases and l' H20 decreases as the concentration of the strong acid increases, so that Δφ increases monotonically.

On the other hand, when the sample solution is a strong base solution such as water, the ionization reaction of H20 in the sample solution: 2H20* R30
"+ OH-(XI) is generated, so this reaction and the reaction of formula CI) are combined 02- (in oxygen ion conductive ceramic membrane) + 8
20 (in sample solution):: 20H- (in sample solution>
Formula 0 (where the reaction of (Xlr) is occurring (
By treating the reaction of XI[) in the same manner as the reaction of formula (I).

Δφ=φH2O −(J'02−+J' H,,0−2J” □H−)
/2F-RT(log, aoH-)/T0RT(l
ogl, ILH20)/2F (XI), and according to the formula <yx>, as the concentration of one strong base increases, a - increases and a decreases, so OH)120 At this time, it can be seen that Δφ decreases monotonically.

To summarize the above, in a solution with water in which a strong acid or strong base is dissolved alone at a high concentration, Δφ of the membrane electrode used in the method of the present invention at a constant temperature is 1, not PH. Strong acid or strong f! ! Depends on the type and concentration of the group,
Furthermore, its value increases monotonically as the concentration of a strong acid increases, and decreases monotonically as the concentration of a strong base increases.

The 11M electrode according to the present invention includes a fluid-impermeable membrane made of the most ionically conductive ceramic.

An electrochemical system is provided inside the container, and a terminal electrically connected to the electrochemical system is placed outside the container, but there is no temperature difference between the terminal and the inside of the membrane. Regarding the effect of generating a certain internal potential difference depending on the
Products Research and Development, No. 22, pp. 594-593, 1983 [Nfed
rach, Ind, Eng, Chem-Prod
, Res, Dev, 22, 594-599 (
10 March and 5taddard paper “Zirconia R
1 pH sensor: ZirconiaMe+5brane
pH'3 sensors J.

Also, tree J? #] In the method, the liquid-to-liquid potential generated in the liquid path between the sample solution and the reference electrode liquid 18j depends only on the type and concentration of ions contained in both liquids at a constant temperature. Therefore, at a constant temperature, the terminal voltage between the membrane fttJ4i and the reference electrode, which includes the liquid junction potential and the potential of the membrane m pole, is a strong acid or a strong! ! ! Depends on the concentration of the group.

Therefore, if the region in which the voltage between the terminals monotonically increases or decreases with respect to an increase in the concentration of the strong acid or strong base is used, then by measuring the voltage between the terminals,
The concentration of strong acids or bases can be determined.

Note that the concentration dependence of the strong acid or strong base on the terminal +1jl voltage can be made by selecting the configuration of the liquid path between the electrode liquid of the reference electrode and the sample solution. That is, by selecting the configuration, it is possible to select a region in which the voltage between the terminals monotonically increases or decreases with respect to the concentration of the strong acid or the strong j group so as to include a desired concentration range.

In the above configuration, in the liquid path part, in addition to a direct type in which the sample solution and u'+ are directly connected to the electrode liquid, there is also a type in which an arbitrary aqueous solution can be stored as an intermediate liquid between the sample solution and the electrode liquid. Three or more intermediate chambers are provided, sample #liquid 1 width nJ1 liquid 1 intermediate liquid snow...
There is an indirect type in which the electrodes are arranged in series like the electrode solution. High concentration of acid or a! When measuring the reference electrode over a long period of time, the i! In order to avoid negative effects on the electrode body, it is preferable to use the indirect type. In this case, the intermediate liquid may be of the same type and concentration as the reference electrode, or may be different. Regardless of the configuration of the liquid path, the concentration dependence described above is determined by the type 8 and concentration range of the sample solution and the type and composition of the solution adjacent to the sample solution.

In addition, as shown in the [Examples of the Invention] section below, the inventor used a highly concentrated potassium chloride aqueous solution that is commonly used for salt bridges as a solution adjacent to the sample solution. In some cases, the concentration dependence can be obtained sufficiently well over a wide range, but the following method is also available as one method for selecting the configuration so that the concentration dependence with respect to the terminal voltage becomes a single yJ function. In other words, try
The composition of the solution adjacent to the solution may be selected as follows. That is, as a solution adjacent to the sample solution, a solution in which only the same strong acid or strong base as the sample solution is dissolved at a constant concentration is used. Now, assume that the liquid junction potential between the sample solution and the solution adjacent to the sample solution is Δφ crossing. When the sample solution is a solution with a strong acid H The interfacial potential difference ΔΦ on the surface of the membrane TrL electrode in contact with the sample solution,
The same strong acid H! adjacent to the sample solution! The liquid junction potential Δφ of the sample solution with respect to the solution A (this phase is indicated by n). Here, the wheel wheel of minute i is Ti.

Let the activity of component i in phase j be 7.

Here 'T) 130° + TA, -1 therefore.

Using the average activity &U^ of H8A.

By the way, the expression (stomach) is H, A ten tomi H20, -1830+ A
Because it is! O Δφ= 2F "02-""H2O"-"'0
20)"￥"oge")!30"-1toH@&:4
2o) (X■) From equations (x v'+) and (X■), Δφ+Δφl =-PAc"'02-10"''.=3
JLy, p) RT n 3 layer + 10jce ao3o-210ge aH2° formula (
In X■), when the concentration of ■8A in the sample solution increases, a and 0 decrease.

Δφ+ΔΦ also increases. Similarly, when the sample solution is a solution of a strong base in water, it can be shown that the Δφ+Δφ statement decreases as the concentration of the strong base increases.

Therefore, if the sample solution is a solution of a strong acid and water or a solution of a strong base and water, the same strong acid or only the strong base as the sample solution is added to the solution adjacent to the sample solution at a constant concentration. If a dissolving solution is used, what is the terminal a voltage between the membrane electrode and reference electrode for the concentration of the strong acid or strong base in the sample solution? At this time, by measuring the voltage between the terminals, the concentration of the strong acid or strong base in the sample solution can be determined.

As mentioned above, the sample solution to which this invention can be used has a hydrogen ion activity or an average activity of a strong acid,
Or the average activity of hydroxyl ion or strong base is single g! ! A necessary condition was that the solution had a concentration range of strong acids or strong bases in which the activity of water increases and the activity of water decreases monotonically. There are solutions of strong acids or strong bases and water that do not meet this requirement, such as sulfuric acid or nitric acid where M is close to 1096. However, even in such a case, the method of the present invention can be applied by simply diluting the sample solution with water at a constant ratio that allows dilution to the maximum concentration that satisfies the above conditions. become. In this case, it is also possible to measure the concentration from the pH with a glass electrode by diluting it with water at a fixed ratio in the same way, but the amount of water is several to 100 times larger than when using this IJJ method. However, there are disadvantages in that the error associated with dilution is also larger.

As long as the above-mentioned restrictions regarding activity and average activity are satisfied, the sample solution to which this invention can be used will contain not only one strong acid or strong base alone, but also hydrogen ions and A solution with water that contains only impurities to such an extent that the effect on water activity can be ignored may be sufficient.

Although it depends on the required accuracy of the concentration measurement, it is possible to include any 6 arbitrary salts as such coexisting substances, subject to the above-mentioned restrictions on the influence on the activity.

This point measures the electrical conduction by all ions present in the solution. This method has a wider range of applicability than the conventional method of determining the concentration from electrical conductivity.

According to the above-described effects of the method of the present invention, the method of the present invention can measure up to high concentrations by applying potentiometric measurement regardless of the type of strong acid or strong base. Furthermore, even if air bubbles occur in the sample solution, such air bubbles do not change the concentration of the strong acid or strong base, so they do not interfere with the implementation of the method of the present invention, and the method of the present invention cannot be performed using the potentiometric method. So J! ! This means that the measurements can be carried out automatically.

[Embodiment of the Invention] An embodiment of the method of the present invention will be specifically described based on FIG. Figure t51 shows an example of the basic configuration of a measuring device used when applying the method of the present invention.

In the figure, I14 constant let is roughly divided into a measurement tank 1 and other electrical processing parts. I! 4. In the fixed tank 1, an indicator electrode 2. It is immersed into the reference electrode 3 and the terminal for measuring liquid temperature, and further.

A liquid inlet pipe 5 and a liquid outlet pipe S are provided. All of these components are made of materials that have sufficient corrosion resistance against the sample solution. In the measuring tank 1, a sample solution is introduced into the tank through an inlet pipe 5 and discharged to the outside of the tank through an outlet pipe 6. On the other hand, the measurement tank! In electrical processing parts other than
The indicator electrode 2 and reference electrode 3 are each connected via a lead wire to an impedance converter 7 for detecting the voltage between the two electrodes, and the liquid temperature measurement terminal 4 is connected to a signal converter 8 via a lead wire. has been done. Furthermore, the impedance converter 7 and the signal converter 8 are each connected via lead wires to a concentration calculator 9 built in a microcomputer. Then, the concentration calculator e converts the voltage between the terminals and the signal! By comparing the output voltage of I8 with pre-programmed reference data, the concentration of strong acid or strong base in the sample solution is calculated and output. Note that the measurement tank 1 and the indicator electrode 2. Portions of the reference electrode 3 and the liquid temperature measuring terminal protruding from the measuring tank 1.

And impedance conversion between indicator electrode 2 and reference electrode 3! It is preferable that all the lead wires connected to the terminal 17 be shielded to prevent induction of static electricity 1, and that the shield be grounded.

If necessary, the liquid inlet pipe 5 and the liquid outlet pipe 6. In addition, the part of the lead wire connected to the liquid temperature measurement terminal 4 near the measurement tank 1 is also shielded to prevent static induction. It is desirable to cover the tank with heat insulating material.

In order to measure the concentration of a sample solution using such a measuring device, first, a multi-point voltmeter R device is installed in place of the concentration calculator 3, and the impedance converter 7 and signal converter 8 are Each output voltage is inputted to the recording device, and then a solution of a strong acid or strong base with water with a known 1:i degree is added to the liquid input tube 5 while keeping the temperature constant.
Measuring tank! The liquid is introduced into the tube and discharged from the drain pipe 6 to allow the liquid to flow through the impedance converter 7 and signal conversion! ! Measure the combination of each output voltage value with 8. In this way, similar measurements are made on solutions of wood with strong acids or strong bases at different temperatures and concentrations. A program in which the combination of the steady output voltage values of the impedance converter 7 and the signal converter 8 for each temperature and concentration of s1 is input as reference data is input into the concentration calculator 3; With respect to the data, a concentration calculator 9 compares the combination of output voltages of the impedance converter 7 and the signal converter 8 in the sample 4 solution, and selects the concentration when it matches the reference data,
After inputting a program to perform the calculation to be output, remove a*at and install the concentration calculator 3 again.

Then, a sample solution of unknown concentration is allowed to flow through the sample solution in the same manner as the above-mentioned solution of known concentration. In this state, the indicator electrode 2 and reference electrode W
The terminal voltage between 3 and 3 passes through an impedance converter 7,
On the other hand, a signal related to the liquid temperature detected by the liquid temperature measuring terminal 4 is converted into a voltage by a signal converter 8, and both are input to a concentration calculator 9. As stated in the [Summary of the invention] section,
At a constant temperature, the voltage between the indicator electrode 2, which is an M electrode, and the reference electrode 3 depends on the concentration of the strong acid or strong base in the sample solution. therefore.

The concentration calculator 3 uses the reference data obtained above at °C1, the impedance converter 7 obtained from the sample solution, and the signal conversion g! 8 output signal voltages are compared, and the concentration corresponding to the sample solution is selected and output. More than 1 in this way? The concentration of the sample solution can be continuously and automatically measured by setting the sample temperature.

Experiment I to confirm the effectiveness of this invention method
(2) was carried out using the measuring device shown in FIG. The apparatus shown in FIG. 2 is basically the same as that shown in FIG. 1 (the same components as in FIG. Instead, a 2-pen XY voltmeter lO is arranged, and two liquid storage tanks 11, 12. Flow path switching valve 13
．． 14 and pump! 5 was newly installed. In such a configuration, the sample solution in one liquid storage tank 11 (12) is transferred to the liquid storage tank 11 (12), the flow path switching valve 13 (14), the pump 15. The measurement tank 1 and the original storage tank 11 (12) are circulated in this order, and the sample solution in the other storage tank 4612 (11) is circulated in the same way by switching the flow path using the flow path switching valve 13.14. It is now possible to make reversible changes.

In such a measuring device, the indicator electrode 2 has an outer diameter of 30.0 ms and is made of 6 mol% Y2O3 stabilized ZrO2.
+.

Wall thickness 0.711. A membrane electrode formed by disposing a commercially available potassium chloride saturated silver chloride electrode and a phthalate standard ml liquid solution specified in JIS K8474 as an electrochemical system was placed in a Tamman tubular firing tube with a length of 220 mm. In addition, as the reference electrode 3, a double-junction type commercially available potassium chloride saturated silver silver chloride electrode (the intermediate chamber contained potassium chloride crystals and a saturated potassium chloride aqueous solution) was used to prevent the sample solution from mixing with the electrode solution. ) were used respectively. In addition, for the terminal reef for liquid temperature measurement, a commercially available SO5304 sheathed PT resistance thermometer sheathed tube I: PT gloss plated was used, and the flow path + JJ switching valve 13° and the pump 15 are the wetted parts. A material made of polytetrafluoroethylene resin was used. Furthermore, a measurement tank! The liquid inlet pipe 5, liquid outlet pipe 8, and other piping were made of polytetrafluoroethylene resin.

Then, the indicator electrode 2 was installed in the measuring tank 1 so that the ceramic film portion thereof was exposed over a length of 200 mm. In addition, considering the influence of thermoelectromotive force based on the temperature distribution generated in the stabilized ZrO2 firing tube of the indicator electrode 2, the mounting position of the indicator electrode 2 and the amount of solution inside the electrode were strictly controlled. On the other hand, the volume of the measuring rod was 5001 cm, and the circulation rate of the sample solution was 917 sin. Further, the measurement temperature was maintained at 25° C., and the impedance converter used had an input resistance of 10 Ω.

Experiment I Use hydrochloric acid with a concentration of 4 mol/l (volume molarity display, the following mol/value is the same) and sodium aqueous solution with a concentration of 4 mol/l as the test solution, and after pouring the sample solution into the measurement tank 1. Immediately, the change over time in the terminal voltage between the indicator electrode and the reference electrode was measured, and the results are shown as solid lines in Figure 3 (hydrochloric acid) and Figure 4 (sodium hydroxide), respectively.

For comparison, an experiment was conducted in exactly the same manner as above, except that a commercially available glass electrode was used as the indicator electrode 2.
The results are shown by broken lines in the tJSa diagram and FIG. 4, respectively.

As will be seen, the glass electrode exhibits a slower response than the membrane electrode according to the present invention, and is particularly noticeable in hydrochloric acid. However, the membrane electrode according to the present invention does not respond to the terminal-terminal voltage It can be seen that no delay was observed, and the response was better than that of the glass electrode.

Experiment ■ Using hydrochloric acid and sodium hydroxide aqueous solutions with different concentrations as sample solutions, we investigated the reproducibility of the response of the terminal voltage to concentration fluctuations. That is, 5 mol/1 each
(A) and 10 mol/1 (B) are put into the liquid storage tanks 11 and 12, and the flow path switching valve +3. The voltage change was investigated by switching I every 24 hours. The results are shown in Figure @5 (hydrochloric acid) and Figure !86 (sodium hydroxide).

The time lag between each channel switching-valve switching and the start of actual potential change has been removed from the diagram. In both cases, a transient change is seen in the voltage between the terminals, but this is thought to be caused by the time it takes to replace the liquid in the measurement tank 1. When a glass electrode is used in a highly concentrated strong acid or strong base solution.

Based on these results, it is known that the reproducibility of the potential response is poor or is getting worse.

It can be seen that when the membrane electrode according to the present invention is used, the voltage between the terminals responds to concentration fluctuations with good reproducibility.

Experiment ■ Trial 14 Using each aqueous solution of hydrochloric acid, perchloric acid, sodium hydroxide, and potassium hydroxide as the In solution, the relationship between the concentration of these sample solutions and the voltage between the terminals was investigated.

The obtained results are shown in Figure 7 (hydrochloric acid 20, perchloric acid: φ) and Figure 8 (sodium hydroxide 20, water-uglying potassium: *
)It was shown to. Furthermore, FIGS. 7 and 8 show the indicated value # when the above membrane electrode functions as a hydrogen ion sensor.
A solid line indicating I was obtained by substituting aH20''1 into the above-mentioned formula (IX) and is also shown.

From now on, when the membrane electrode according to the present invention is used in a solution in which a strong acid or a strong base is dissolved in water at a high concentration, it will not function as a hydrogen ion senna, and the voltage between the terminals will be lower than that of the strong acid or strong base. Although it depends on the type of strong base, it can be seen that the concentration of strong acids and strong bases can be measured by the method of the present invention.

[Effects of the Invention 1] As is clear from the above description, the method for measuring the concentration of a strong acid or strong base in a solution with water according to the present invention has the following excellent effects.

(a) Measurement is possible regardless of the type of strong acid or strong base being measured.

This is because the voltage between the terminals of the indicator electrode and the reference electrode can be made to monotonically increase or monotonically decrease depending on the concentration of the strong acid or strong base contained in the sample solution.

(b) Can measure higher concentrations than concentration measurements using glass bowls and poles.

This is because even in the case of a highly concentrated strong acid or strong base solution, unlike glass electrodes, the responsiveness of the voltage between terminals and the reproducibility of the responsiveness do not deteriorate.

(c) Not affected by the generation of bubbles in the sample solution.

5. Bubbles do not change the concentration of strong acids and strong bases, and
This is because the potential of the membrane electrode and the liquid potential between the sample 4 solution and the electrode solution of the reference electrode depend only on the concentration at a constant temperature.

Since the method of the present invention is based on 1M 1-position difference measurement, continuous and automatic measurements can be carried out, and the method has the excellent effects described above, so its industrial value is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the basic configuration of an apparatus for carrying out the method of the present invention, FIG. 2 is a configuration diagram for explaining an embodiment of the present invention, and FIGS. 3 and 4 are diagrams showing terminals. FIGS. 5 and 6 are diagrams showing the responsivity of voltage; FIGS. 5 and 6 are diagrams showing the reproducibility of the responsivity of the voltage between terminals; FIG. tPJ7 and FIG. 8 are diagrams showing the relationship between concentration and terminal voltage. ! ...Measurement (6, 2... Indicator electrode. 3... Reference electrode, 4... Terminal for measuring liquid temperature. 5... Liquid inlet pipe, 6... Liquid outlet pipe. 7... - Impedance converter. 8... Signal converter, 3... Concentration calculator, 11
．． 12...Liquid storage tank, Figure 1 Figure 2 Figure 3 4 OIo 20 30 Sai7'-'l (h) Closed (min) Figure 7 Dark L (mo7/jri 4th change (moj! /Jl)

Claims (1)

[Claims] 1. An indicator electrode and a reference electrode are immersed in a sample solution consisting of a solution of a strong acid or a strong base in water, and the sample is determined from the voltage between the terminals generated between the indicator electrode and the reference electrode. A method for measuring the concentration of a strong acid or strong base in a solution, the indicator electrode being in contact with a container made of a fluid-impermeable membrane made of oxygen ion conductive ceramics and at least a part of the inner surface of the container. a metal terminal electrically connected to the electrochemical system and extending outside the container, and a constant temperature dependent only on temperature between the metal terminal and the membrane phase. A method for measuring the concentration of a strong acid or strong base in a solution with water, characterized by using a membrane electrode that generates an internal potential difference of . 2. The reference electrode has an electrode liquid of at least 1
It has a structure in which the sample solution and the liquid flow through two intermediate chambers,
2. The method according to claim 1, wherein the solution in the intermediate chamber adjacent to the sample solution is a solution with water that dissolves only a strong acid or strong base of the same type and concentration as the sample solution. 3. The electrochemical system includes an electrolyte aqueous solution with a constant pH connected to at least a portion of the inner surface of the container, and an aqueous solution reference electrode that is at least partially immersed in the electrolyte aqueous solution, or an aqueous solution using the electrolyte aqueous solution as an electrode liquid. The method according to claim 1 or 2, comprising the aqueous solution reference electrode body constituting the aqueous solution reference electrode. 4. The electrochemical system electrically connects a mixture of a metal and an oxide of the metal that is in contact with at least a portion of the inner surface of the container, and an electronic conductor that electrically connects the mixture and the metal terminal. 3. The method according to claim 1, comprising a lead, and a sealing member that isolates the inner surface of the container, the mixture, and the conductive lead from outside air. 5. The electrochemical system electrically connects a mixture of two types of oxides of the same metal with different metal valences that are in contact with at least a portion of the inner surface of the container, and the mixture and the metal terminal. 3. The method according to claim 1, further comprising: a conductive lead having electronic conductivity; and a sealing member that isolates the inner surface of the container, the mixture, and the conductive lead from outside air. 6. The oxygen ion conductive ceramic contains stabilized zirconium oxide, thorium oxide doped with other oxides, cerium oxide doped with other oxides, bismuth oxide doped with other oxides, and other oxides. 6. The method according to claim 1, wherein the lanthanum oxide is selected from the group consisting of doped lanthanum oxide or a solid solution of at least two species selected from said group. 7. The method according to any one of claims 1 to 5, wherein the oxide ion conductive ceramic is stabilized zirconium oxide.