JP2005024408A - Instrument of measuring residual chlorine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a residual chlorine measuring instrument capable of obtaining a constant oxidation-reduction current under a fixed measuring voltage when a residual chlorine concentration is the same, even when a halide ion concentration is fluctuated, and capable of measuring accurately the residual chlorine concentration therein. <P>SOLUTION: This instrument is provided with a detecting electrode 3a immersed into a sample liquid A and rotated, and a counter electrode 2d. The counter electrode 2d is immersed into an electrolyte solution B containing a high concentration of chloride ion. The sample liquid has electrical continuity with the electrolyte solution B, by a filter 2c serving as a liquid junction part. The oxidation-reduction current flowing between the detecting electrode 3a and the counter electrode 2d due to electrolytic reduction of the residual chlorine in the sample liquid A is detected to measure the residual chlorine concentration. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００２９】
（比較例１）
対極が直接試料液に接している従来技術に係る残留塩素測定装置（検知極：金、対極：銀／塩化銀電極）を用いて、水道水から下水処理水相当のハロゲン化物イオンを含む試料液１１〜１４と、海水相当の約３％のＮａＣｌを含む試料液１５〜１７の残留塩素濃度を測定した。測定電圧は０ｍＶとした。
表２に、ａ．各試料の電気伝導率（ＥＣ）、ｂ．ＤＰＤ法により求めた遊離塩素濃度（ＤＰＤ−Ｆ）、ｃ．試料１１、試料１２を、各々ゼロ、スパン液として校正して得られた装置の測定値、ｄ．ｂ（ＤＰＤ−Ｆ）に対するｃ（測定値）の誤差を示す。
表２に示すように、測定電圧を０ｍＶに固定したままでも、水道水から下水処理水相当のハロゲン化物イオンを含む試料液１１、１２で校正した装置で、海水相当の試料液１５〜１７の残留塩素濃度を正確に測定することができた。
【００３０】
【表２】

【００３１】
（実施例２）
第１実施形態の装置（検知極：金、対極：銀／塩化銀電極）を用いて、水道水から下水処理水相当のハロゲン化物イオンを含む試料液３１、３２と、海水相当の約３％のＮａＣｌを含む試料液３３〜３５の残留塩素濃度を測定した。測定電圧は１００ｍＶとした。
表３に、ａ．各試料の電気伝導率（ＥＣ）、ｂ．ＤＰＤ法により求めた結合塩素濃度（ＤＰＤ−Ｂ）、ｃ．試料３１、試料３２を、各々ゼロ、スパン液として校正して得られた装置の測定値、ｄ．ｂ（ＤＰＤ−Ｂ）に対するｃ（測定値）の誤差を示す。
表３に示すように、測定電圧を１００ｍＶに固定したままでも、水道水から下水処理水相当のハロゲン化物イオンを含む試料液３１、３２で校正した装置で、海水相当の試料液３３〜３５の残留塩素濃度を正確に測定することができた。
【００３２】
【表３】

【００３３】
（比較例２）
対極が直接試料液に接している従来技術に係る残留塩素測定装置（検知極：金、対極：銀／塩化銀電極）を用いて、水道水から下水処理水相当のハロゲン化物イオンを含む試料液４１〜４２と、海水相当の約３％のＮａＣｌを含む試料液４３〜４５の残留塩素濃度を測定した。測定電圧は−１００ｍＶとした。
表２に、ａ．各試料の電気伝導率（ＥＣ）、ｂ．ＤＰＤ法により求めた結合塩素濃度（ＤＰＤ−Ｂ）、ｃ．試料４１、試料４２を、各々ゼロ、スパン液として校正して得られた装置の測定値、ｄ．ｂ（ＤＰＤ−Ｂ）に対するｃ（測定値）の誤差を示す。
表４に示すように、水道水から下水処理水相当のハロゲン化物イオンを含む試料液４１、４２で校正した装置で、測定電圧を−１００ｍＶに固定したままで、海水相当の試料液４３〜４５の残留塩素濃度を測定すると、０．１ｍｇ／Ｌ以上の誤差が生じた。
【００３４】
【表４】

【００３５】
上記実施例１、２より、本発明の装置を用いれば、測定電圧を固定したままで、塩化物イオン濃度にかかわらず、遊離塩素、結合塩素共に正確に測定できることが確認された。
これに対して、従来装置を用いた比較例１、２によれば、測定電圧を固定したままででは、塩化物イオン濃度の変化によって結合塩素の測定値に誤差が生じてしまうことが確認された。
【００３６】
【発明の効果】
本発明の残留塩素測定装置によれば、試料液中のハロゲン化物イオン濃度が変動しても、同じ残留塩素濃度であれば測定電圧を固定したままで一定した酸化還元電流が得られ、残留塩素濃度の正確な測定が可能となる。
【図面の簡単な説明】
【図１】本発明の第１実施形態を示す概略図である。
【図２】本発明の第２実施形態を示す概略図である。
【符号の説明】
１・・水槽、２・・対極ユニット、３・・検知極ユニット、２ｄ・・対極、
２ｅ・・塩化ナトリウム錠剤、２ｆ・・対極、６・・電源、７・・電流計、
Ａ・・試料液、Ｂ・・電解質溶液[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a so-called reagentless type residual chlorine measuring apparatus that directly detects residual chlorine in a sample solution without replacing it with iodine or bromine.
More specifically, the present invention relates to a residual chlorine measuring apparatus capable of measuring a stable residual chlorine concentration regardless of the halide ion concentration in a sample solution.
[0002]
[Prior art]
Chlorination is performed to disinfect various types of water such as clean water, sewage, industrial water, waste water, food washing water, and pool water. The chlorinating agent used in this chlorination must be put in a sufficient amount to disinfect the water to be disinfected, but if it is added too much, it will adversely affect the environment and harm the human body. It is not desirable to give. Therefore, measurement of the residual chlorine concentration of water charged with a chlorinating agent is performed.
[0003]
Residual chlorine includes hypochlorous acid (free residual chlorine) produced by the dissolution of the chlorine agent in water, and chloroamine (bound chlorine) generated by combining it with ammonia. Is the total residual chlorine concentration.
[0004]
As a manual analysis method for measuring the residual chlorine concentration, an o-tolidine colorimetric method (OT method), a diethyl-p-phenylenediamine colorimetric method (DPD method), an iodine titration method, or the like is used. However, since the manual analysis method is complicated and measurement data can be obtained only intermittently, a residual chlorine measuring device has been conventionally used. This residual chlorine measuring device is classified into a so-called reagent type residual chlorine measuring device and a reagentless type residual chlorine measuring device.
[0005]
Reagent-type residual chlorine measuring device is a potassium iodide solution (or potassium bromide solution) added to a sample, and iodine (or bromine) released according to the residual chlorine concentration is negatively measured with respect to the counter electrode. The residual chlorine concentration is obtained by amplifying the reduction current (diffusion current) when it is subjected to electrolytic reduction by the detection electrode to which iodine is applied and becomes iodine ion (or bromine ion).
[0006]
On the other hand, the reagentless residual chlorine measuring device does not replace residual chlorine with iodine etc., but electrolyzes the residual chlorine itself in the sample solution as it is, so that the oxidation-reduction current flowing between the detection electrode and the counter electrode Is detected and the redox current is measured.
In the reagentless type residual chlorine measuring device, free residual chlorine and bound chlorine are detected together although there is a difference in sensitivity. However, in the drinking water, most of the residual chlorine is free residual chlorine. Used as a device.
Recently, it has also been proposed to use this reagentless type residual chlorine measuring device for sewage effluent water in which most of the residual chlorine is bound chlorine (see Patent Document 1).
[0007]
This reagentless type residual chlorine measuring device has an advantage that the configuration of the measuring device is not complicated because basically no reagent is required, but there is a problem that it is easily affected by coexisting components. Above all, it is easily influenced by halide ions such as electrolyte ions, particularly chloride ions, and if the halide ion concentration varies greatly, the plateau region in the polarogram changes. Therefore, it is necessary to set an appropriate measurement voltage according to the halide ion concentration.
Therefore, the electrical conductivity corresponding to the halide ion concentration has been measured, and an appropriate measurement voltage has been obtained from this electrical conductivity value (see Patent Document 2). Since the apparatus of Patent Document 2 has a function of automatically measuring electrical conductivity, it has a feature that it is not necessary to bring back the sampled sample solution to perform measurement.
[0008]
[Patent Document 1]
JP 2000-275214 A [Patent Document 2]
Utility Model Registration No. 2596034 Publication [0009]
[Problems to be solved by the invention]
However, in the apparatus of Patent Document 2, electric conductivity measurement is performed without using a dedicated electric conductivity sensor, so that the apparatus has a complicated circuit configuration.
In addition, even if the electrical conductivity of the sample solution is automatically and continuously measured, in the case of a sample solution whose halide ion concentration is constantly changing, such as sewage effluent near the estuary where seawater is mixed, It is difficult to apply the corresponding measurement voltage in real time. Therefore, it has been difficult to accurately and continuously measure the residual chlorine concentration of the sample liquid in which the halide ion concentration constantly changes.
[0010]
In view of the above circumstances, the present invention provides a residual chlorine measuring device that can accurately and continuously measure the residual chlorine concentration regardless of variations in the halide ion concentration and does not require a complicated circuit configuration such as changing the measurement voltage. It is an issue to provide.
[0011]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention formed an electrolyte solution layer containing halide ions around the counter electrode, and conducted with the sample solution through this electrolyte solution layer. It was found that a constant plateau region was obtained regardless of the halide ion concentration of the liquid, and that residual chlorine measurement was possible without changing the measurement voltage.
It is presumed that the above problem can be solved by the present invention because the potential of the counter electrode is stabilized by stabilizing the halide ion concentration around the counter electrode.
[0012]
That is, the present invention is a residual chlorine measuring device for measuring a residual chlorine concentration in a sample solution, wherein a detection electrode immersed in the sample solution and a sample solution in contact with the detection electrode are attached to the surface of the detection electrode. Liquid flow generating means for relatively flowing, a counter electrode electrically conducting with the sample solution, and an electrolyte solution layer forming means for forming an electrolyte solution layer containing halide ions around the counter electrode, Provided is a residual chlorine measuring device for measuring a residual chlorine concentration by detecting an oxidation-reduction current flowing between the detection electrode and the counter electrode by electrolytic reduction of residual chlorine in the sample solution. To do.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, the oxidation / reduction current flowing between the detection electrode and the counter electrode is detected by reducing the chlorine itself without replacing the chlorine with iodine or bromine.
Examples of the detection electrode in the present invention include a gold electrode, an alloy electrode containing gold as a main component, a platinum electrode, and a glassy carbon electrode. Moreover, a silver / silver chloride electrode, a platinum electrode, etc. are mentioned as a counter electrode in this invention.
The measurement voltage applied between the detection electrode and the counter electrode is not particularly limited. The voltage within the plateau region determined by the type of detection electrode and counter electrode to be combined, whether free chlorine or combined chlorine is measured, etc. Is preferred.
[0014]
For example, when a detection electrode of a gold electrode and a counter electrode of a silver / silver chloride electrode are used in combination, it is preferable to apply a measurement voltage of +100 to +400 mV to the detection electrode with reference to the counter electrode. If the main purpose is measurement of free chlorine, it is more preferable to apply a measurement voltage of +200 to +300 mV when the detection electrode of the gold electrode and the counter electrode of the silver / silver chloride electrode are used in combination. . If the main purpose is measurement of bound chlorine, it is more preferable to apply a measurement voltage of +100 to +200 mV when the detection electrode of the gold electrode and the counter electrode of the silver / silver chloride electrode are used in combination. .
Note that the measurement voltage may be 0 mV. That is, a polar system that applies a voltage between the detection electrode and the counter electrode or a galvanic system that does not apply a voltage may be used.
[0015]
The residual chlorine measuring apparatus of the present invention includes means for forming an electrolyte solution layer containing halide ions around the counter electrode.
The halide ion is preferably a chloride ion, but may be a bromide ion or an iodide ion. Moreover, as an electrolyte containing a halide ion, a sodium salt and a potassium salt are particularly preferable.
There is no particular restriction on the concentration of halide ions in the electrolyte solution layer, but it is preferable to contain a higher concentration of halide ions than the sample solution, and to contain a much higher concentration of halide ions than the sample solution. More preferred. A saturated solution such as a saturated sodium chloride solution or a saturated potassium chloride solution is particularly preferable. Thereby, even if the halide ion concentration in the sample solution varies, it can be suppressed that the halide ion concentration in the electrolyte solution layer substantially varies.
The electrolyte solution layer may be liquid, sol, gel, or solid.
[0016]
As the electrolyte solution layer forming means, an electrolyte solution container containing a halide ion therein is accommodated, and an electrolyte solution container having a liquid junction for electrically connecting the electrolyte solution to the sample solution is employed. The electrolyte solution container may be immersed in the sample solution, and the counter electrode may be immersed in the electrolyte solution in the electrolyte solution container.
The liquid junction used here is for electrically connecting the internal liquid and the sample liquid. Examples of the liquid junction include known liquid junctions such as porous ceramics, resins, sleeves, and pinholes, but porous ceramics and resins are preferable.
[0017]
Further, the electrolyte solution layer forming means may be means for supplying an electrolyte solution containing halide ions around the counter electrode. For example, the electrolyte solution is allowed to flow out of a filter placed near the counter electrode, or an electrolyte that dissolves in a sample solution such as a sodium chloride tablet or a potassium chloride tablet is placed near the counter electrode. it can.
Further, the electrolyte solution layer forming means may be a gel electrolyte solution layer wound around the counter electrode surface.
[0018]
The oxidation-reduction current measured in the present invention is transported to the surface of the detection electrode only by natural diffusion due to a concentration gradient in a layer called a diffusion layer having a constant thickness, and the reduction target chlorine is reduced on the surface. The diffusion current that flows when
[0019]
In order to obtain an oxidation-reduction current (diffusion current) according to the chlorine concentration, it is necessary to constantly update the diffusion layer. Since the residual chlorine measuring device of the present invention includes liquid flow generating means for causing the sample liquid in contact with the detection electrode to flow relative to the surface of the detection electrode, the diffusion layer is always kept constant, Chlorine is supplied to the sensing electrode according to its concentration.
[0020]
Examples of the liquid flow generating means include a detection electrode driving means for rotating or vibrating the detection electrode, and a means for causing the sample liquid to flow with a pump or the like while the detection electrode is kept stationary. The detection electrode used by rotating is called a rotating electrode, and the electrode used by vibrating is called a vibrating electrode. These electrodes rotate and vibrate at a linear velocity much higher than the normal flow rate of the sample liquid. For this reason, a stable diffusion layer can be formed regardless of the sample liquid flow rate, and the measurement value due to fluctuations in the sample liquid flow rate is not easily affected. It is also possible to rotate and vibrate the detection electrode in the cleaning bead, and in this case, it is possible to easily prevent dirt from adhering to the detection electrode.
[0021]
In rotating electrodes, there are a method of using a mercury contact and a method of preventing the twisting of the lead wire by alternately switching the rotation direction in order to pull out the lead wire from the rotating detection electrode without cutting it. As shown in Japanese Patent No. 4566, a method in which the detection pole is moved circularly by moving the support of the detection pole in a chopped form without rotating is preferable. As for the vibrating electrode, there are various methods such as a method of vibrating the detection pole with an external vibrator (see Japanese Utility Model Publication No. 62-41240), a method of vibrating using a built-in electromagnet (Japanese Utility Model Publication No. 6-765). In this invention, any system may be adopted.
[0022]
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes a water tank filled with the sample liquid A, and the counter electrode unit 2 and the detection electrode unit 3 are immersed in the sample liquid A in the water tank 1. To the sample solution A, a reagent containing halide ions such as iodide ions and bromide ions is not added.
[0023]
The counter electrode unit 2 includes a support tube 2a, a lid 2b covering the top of the support tube 2a, a filter 2c attached to an opening at the bottom of the support tube 2a, and a counter electrode 2d inserted into the support tube 2a. And the sodium chloride tablet 2e filled in the support tube 2a.
The detection pole unit 3 includes a detection pole 3a and a holder 3b that supports the detection pole 3a. The holder 3b is rotated or vibrated by detection pole driving means such as a motor (not shown). .
The detection electrode 3a and the counter electrode 2c are connected via a conducting wire 4. In addition, a power source 6 that applies a constant voltage between the detection electrode 3a and the counter electrode 2c and an ammeter 7 that detects an electrolytic current flowing between the detection electrode 3a and the counter electrode 2c are interposed in the lead wire 4. ing.
[0024]
In the apparatus according to the present embodiment configured as described above, a part of the sample liquid A flows into the support tube 2a via the filter 2c, whereby the sodium chloride tablet 2e is dissolved in the sample liquid A. As a result, the electrolyte solution B is generated. The chloride ion concentration of the electrolyte solution B can be much higher than the chloride ion concentration of the sample solution A.
The residual chlorine concentration is measured by the apparatus according to the present embodiment by applying a predetermined measurement voltage between the electrodes 2c and 3a in a state where the holder 3b is rotated or vibrated by the detection electrode driving means. At this time, the filter 2c acts as a liquid junction that electrically connects the sample solution A and the electrolyte solution B. Thereby, the oxidation-reduction current due to the reduction of chlorine on the surface of the detection electrode 3a is detected.
In the present embodiment, the counter electrode 2d is immersed in the electrolyte solution B, and the obtained oxidation-reduction current is obtained by measuring the residual chlorine concentration of the sample solution at a constant measurement voltage regardless of the variation of the halide ion concentration of the sample solution A. Is obtained as a value corresponding to. Therefore, it is possible to measure the residual chlorine concentration accurately and continuously.
[0025]
(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.
2, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. 1, and detailed descriptions thereof are omitted.
In the present embodiment, the counter electrode 2f is not inserted into the support tube 2a but is wound around the outside of the filter 2c.
[0026]
In the apparatus according to the present embodiment, the electrolyte solution B generated by dissolving the sodium chloride tablet 2e in the sample solution A flows out through the filter 2c. Thereby, an electrolyte solution layer having a chloride ion concentration much higher than that of the sample solution A is formed around the counter electrode 2f.
The residual chlorine concentration is measured by the apparatus according to the present embodiment by applying a predetermined measurement voltage between the electrodes 2c and 3a in a state where the holder 3b is rotated or vibrated by the detection electrode driving means. Thereby, the oxidation-reduction current due to the reduction of chlorine on the surface of the detection electrode 3a is detected.
In the present embodiment, the counter electrode 2d is in contact with the electrolyte solution layer formed by the electrolyte solution B flowing out, and the obtained redox current is constant regardless of the variation in the halide ion concentration of the sample solution A. Is obtained as a value corresponding to the residual chlorine concentration of the sample solution. Therefore, it is possible to measure the residual chlorine concentration accurately and continuously.
[0027]
【Example】
(Example 1)
Using the apparatus of the first embodiment (detection electrode: gold, counter electrode: silver / silver chloride electrode), sample solutions 1 to 4 containing halide ions equivalent to sewage treated water from tap water, and about 3% equivalent to seawater The residual chlorine concentration of the sample liquids 5 to 8 containing NaCl was measured. The measurement voltage was 200 mV.
In Table 1, a. Electrical conductivity (EC) of each sample, b. Free chlorine concentration (DPD-F) determined by DPD method, c. Measured values of the apparatus obtained by calibrating Sample 1 and Sample 2 as zero and span solutions, respectively; d. The error of c (measured value) with respect to b (DPD-F) is shown.
As shown in Table 1, even with the measurement voltage fixed at 200 mV, the sample solution 1 or 2 containing halide ions equivalent to sewage treated water from tap water was calibrated. Residual chlorine concentration could be measured accurately.
[0028]
[Table 1]

[0029]
(Comparative Example 1)
Sample solution containing halide ions equivalent to sewage treated water from tap water using a conventional residual chlorine measuring device (detection electrode: gold, counter electrode: silver / silver chloride electrode) with the counter electrode in direct contact with the sample solution Residual chlorine concentrations of 11 to 14 and sample solutions 15 to 17 containing about 3% NaCl equivalent to seawater were measured. The measurement voltage was 0 mV.
In Table 2, a. Electrical conductivity (EC) of each sample, b. Free chlorine concentration (DPD-F) determined by DPD method, c. Measured values of the apparatus obtained by calibrating Sample 11 and Sample 12 as zero and span solutions, respectively; d. The error of c (measured value) with respect to b (DPD-F) is shown.
As shown in Table 2, even with the measurement voltage fixed at 0 mV, the sample liquids 11 and 12 containing halide ions equivalent to sewage treated water from tap water were calibrated with sample liquids 15 to 17 equivalent to seawater. Residual chlorine concentration could be measured accurately.
[0030]
[Table 2]

[0031]
(Example 2)
Using the apparatus of the first embodiment (detection electrode: gold, counter electrode: silver / silver chloride electrode), sample solutions 31 and 32 containing halide ions equivalent to sewage treated water from tap water, and about 3% equivalent to seawater The residual chlorine concentration of the sample liquids 33 to 35 containing NaCl was measured. The measurement voltage was 100 mV.
In Table 3, a. Electrical conductivity (EC) of each sample, b. Combined chlorine concentration determined by DPD method (DPD-B), c. Measured values of devices obtained by calibrating Sample 31 and Sample 32 as zero and span solutions, respectively. D. The error of c (measured value) with respect to b (DPD-B) is shown.
As shown in Table 3, even when the measurement voltage was fixed at 100 mV, the sample liquids 31 and 32 containing halide ions equivalent to sewage treated water from tap water were calibrated. Residual chlorine concentration could be measured accurately.
[0032]
[Table 3]

[0033]
(Comparative Example 2)
Sample solution containing halide ions equivalent to sewage treated water from tap water using a conventional residual chlorine measuring device (detection electrode: gold, counter electrode: silver / silver chloride electrode) with the counter electrode in direct contact with the sample solution Residual chlorine concentrations of sample solutions 43 to 45 containing 41 to 42 and about 3% NaCl equivalent to seawater were measured. The measurement voltage was −100 mV.
In Table 2, a. Electrical conductivity (EC) of each sample, b. Combined chlorine concentration determined by DPD method (DPD-B), c. Measured values of the apparatus obtained by calibrating Sample 41 and Sample 42 as zero and span solutions, respectively; d. The error of c (measured value) with respect to b (DPD-B) is shown.
As shown in Table 4, sample liquids 43 to 45 corresponding to seawater were calibrated with sample liquids 41 and 42 containing halide ions equivalent to sewage treated water from tap water, with the measurement voltage fixed at −100 mV. When the residual chlorine concentration was measured, an error of 0.1 mg / L or more was generated.
[0034]
[Table 4]

[0035]
From Examples 1 and 2 above, it was confirmed that if the apparatus of the present invention was used, both free chlorine and bound chlorine could be measured accurately regardless of the chloride ion concentration with the measurement voltage fixed.
On the other hand, according to Comparative Examples 1 and 2 using the conventional apparatus, it was confirmed that an error occurred in the measured value of the combined chlorine due to the change in the chloride ion concentration with the measurement voltage fixed. It was.
[0036]
【The invention's effect】
According to the residual chlorine measuring apparatus of the present invention, even if the halide ion concentration in the sample solution fluctuates, a constant oxidation-reduction current can be obtained with the measurement voltage fixed while the residual chlorine concentration is the same. The concentration can be accurately measured.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a first embodiment of the present invention.
FIG. 2 is a schematic view showing a second embodiment of the present invention.
[Explanation of symbols]
1. ・ Water tank, 2. ・ Counter electrode unit, 3. ・ Detection electrode unit, 2d ・ ・ Counter electrode,
2e ... Sodium chloride tablets, 2f ... Counter electrode, 6 ... Power supply, 7 ... Ammeter,
A ... Sample solution, B ... Electrolyte solution

Claims (4)

A residual chlorine measuring device for measuring the residual chlorine concentration in a sample liquid,
A sensing electrode immersed in the sample solution;
A liquid flow generating means for causing the sample liquid in contact with the detection electrode to flow relative to the surface of the detection electrode;
A counter electrode in electrical communication with the sample solution;
An electrolyte solution layer forming means for forming an electrolyte solution layer containing halide ions around the counter electrode;
A residual chlorine measuring device for measuring a residual chlorine concentration by detecting an oxidation-reduction current flowing between the detection electrode and the counter electrode by electrolytic reduction of residual chlorine in the sample solution. The electrolyte solution layer forming means is an electrolyte solution container having a liquid junction portion for containing the electrolyte solution therein and electrically connecting the electrolyte solution to the sample solution, and the electrolyte solution container The residual chlorine measuring device according to claim 1, wherein the counter electrode is immersed in the electrolyte solution in the electrolyte solution container while being immersed in the sample solution. 2. The residual chlorine measuring apparatus according to claim 1, wherein the electrolyte solution layer forming means is means for supplying the electrolyte solution around the counter electrode. The residual chlorine measuring device according to claim 1, wherein the electrolyte solution contains a higher concentration of halide ions than the sample solution.

Images