JP2016114376A - Solid-state residual chlorine sensor and water meter having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a passive solid-state residual chlorine sensor having a simple structure, and a water meter having the same.SOLUTION: A solid-state residual chlorine sensor 10 comprises a first electrode 11, a second electrode 12, and a voltmeter 13 connected to the first electrode 11 and the second electrode 12. A metal constituting the first electrode 11 is more responsive to free residual chlorine in tap water than a metal constituting the second electrode 12. Electrode potential of the metal constituting the first electrode 11 and that of the metal constituting the second electrode 12 vary similarly with variation of water quality factors of the tap water and environmental factors.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a solid-type residual chlorine sensor applicable to a water meter and a water meter equipped with the same.

Disinfection of tap water is based on Article 17-3 of the Water Supply Law Enforcement Regulations (Ministry of Health, Labor and Welfare) based on Article 22 of the Water Supply Law. Chlorine disinfection to maintain at least 0.4 mg / L in the case of chlorine (provided that the supplied water may be significantly contaminated by pathogenic organisms or suspected of being contaminated by pathogenic organisms) The free residual chlorine in water at the faucet when there is a risk of containing a large amount of such organisms or substances shall be 0.2 mg / L or more (1.5 mg / L in the case of combined residual chlorine). Yes.
At present, the chlorine concentration is controlled at the water purification plant so that the concentration of free residual chlorine contained in the water at the faucet is within the above range, and the free residual chlorine contained in tap water is close to the faucet. Not managing the concentration.

Conventionally, a constant potential electrolysis method has been used as a method for measuring the concentration of free residual chlorine in tap water. The constant potential electrolysis method is a method for measuring a change in current caused by applying a specific electrolytic potential and oxidizing / reducing a target substance.
In addition, the spectrophotometric method, which has become the mainstream at the end of water supply, etc., measures the concentration of free residual chlorine by adding a coloring reagent to tap water and observing the degree of coloring caused by the reaction between the coloring reagent and chlorine. It is. For example, a coloring reagent is added to a standard solution (tap water) in which the concentration of free residual chlorine is known, the free residual chlorine in the standard solution is colored, and the absorbance of that color is measured by absorptiometry, Investigate the relationship between free residual chlorine concentration and absorbance. The relationship between the concentration of free residual chlorine and the absorbance was repeatedly examined by changing the concentration of free residual chlorine in the standard solution. Based on the obtained results, a calibration indicating the relationship between the concentration of free residual chlorine and the absorbance. Create a line. After that, a coloring reagent is added to tap water (sample) whose concentration of free residual chlorine is not known, the free residual chlorine in the sample is colored, the absorbance of the color is measured by absorptiometry, and the obtained absorbance Is applied to the calibration curve to obtain the concentration of free residual chlorine in the sample. Thus, with the absorptiometry, it was difficult to always observe the concentration of free residual chlorine in tap water.

In addition, the constant-potential electrolysis method requires a large amount of power in order to pass a current through tap water, and thus consumes a large amount of power. Therefore, it is difficult to operate a residual chlorine sensor to which a constant potential electrolysis method is applied that is provided in the middle of a water pipe with a battery having a limited capacity for a predetermined period (for example, 8 years or more).
Therefore, an electrode type sensor that operates without requiring energy such as electric power has been proposed. Specifically, it is composed of a silver-silver chloride electrode, having a first electrode serving as an anode, and a second electrode comprising a platinum electrode serving as a cathode, and these two electrodes are connected to tap water. An electrode-type sensor that measures free residual chlorine in tap water by using an electromotive force generated between two electrodes by dipping has been proposed (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 9-72879

  The electrode-type sensor of Patent Document 1 has a problem that the standard electrode potential is lower than that of the second electrode and the third electrode made of a gold electrode is provided, and the structure is complicated.

  This invention is made | formed in view of the said situation, Comprising: It aims at providing a non-feed-type solid-type residual chlorine sensor with a simple structure, and a water meter provided with the same.

The solid-type residual chlorine sensor of the present invention includes a first electrode, a second electrode, and a voltmeter connected to the first electrode and the second electrode, and the metal constituting the first electrode is: Reactivity to free residual chlorine in tap water is higher than that of the metal constituting the second electrode, and the metal constituting the first electrode and the metal constituting the second electrode are water quality factors of the tap water. In addition, the change amount of the electrode potential is approximate to the change amount of the environmental factor.
Here, the water quality factor is a water quality management item that changes the potential of pH, dissolved oxygen concentration, chloride ion concentration, hardness components (Ca, Mg), and the like. The environmental factor is the amount of assembly that changes the electric potential such as the water temperature.

  In the solid-type residual chlorine sensor of the present invention, the metal constituting the first electrode is platinum or titanium, and the metal constituting the second electrode forms a strong passive film in a neutral solution. It is preferable that it is a metal that can be used.

  In the solid-type residual chlorine sensor of the present invention, it is preferable that the pair of electrodes is provided so as to be exposed on an inner surface of a pipe through which the tap water flows.

  In the solid-type residual chlorine sensor of the present invention, it is preferable that the pair of electrodes form part of the pipe.

  In the solid-type residual chlorine sensor of the present invention, it is preferable that portions of the pair of electrodes that are in contact with the tap water are surrounded by a porous body.

  The water meter of the present invention includes the solid-type residual chlorine sensor of the present invention.

  According to the present invention, it is possible to provide a non-feed type solid-type residual chlorine sensor having a simple structure and a water meter equipped with the same.

1 is a schematic diagram showing a first embodiment of a solid-type residual chlorine sensor of the present invention. It is the schematic which shows the usage method of 1st Embodiment of the solid-type residual chlorine sensor of this invention, (a) is sectional drawing in alignment with the longitudinal direction of piping which installed the solid-type residual chlorine sensor, (b) is (a It is sectional drawing which follows the AA line of (). It is a schematic perspective view which shows 2nd Embodiment of the solid-type residual chlorine sensor of this invention. In Experimental example 1, it is a graph which shows the result of having measured the electric potential of the electrode which consists of platinum (Pt). In Experimental example 2, it is a graph which shows the result of having measured the electric potential of the electrode which consists of SUS316. In Experimental example 3, it is a graph which shows the result of having measured the electric potential of the electrode which consists of SUS316L. In Experimental Example 4, it is a graph which shows the relationship between the electric potential of a working electrode, and the pH of a solution. In Experimental Example 5, it is a graph which shows the result of having measured the electrical potential difference of the electrode which consists of platinum (Pt), and the electrode which consists of SUS316L.

Embodiments of a solid-type residual chlorine sensor and a water meter equipped with the same according to the present invention will be described.
Note that this embodiment is specifically described in order to better understand the gist of the invention, and does not limit the present invention unless otherwise specified.

[Solid-type residual chlorine sensor]
(1) 1st Embodiment FIG. 1: is a schematic diagram which shows 1st Embodiment of the solid-type residual chlorine sensor of this invention. FIG. 2 is a schematic view showing a method for using the first embodiment of the solid-type residual chlorine sensor of the present invention, (a) is a cross-sectional view along the longitudinal direction of a pipe in which the solid-type residual chlorine sensor is installed, (b) ) Is a cross-sectional view taken along line AA in FIG.
The solid-type residual chlorine sensor 10 of this embodiment is used for measuring the concentration of free residual chlorine in the tap water 20, and includes a first electrode 11 serving as a cathode, a second electrode 12 serving as an anode, and a first electrode. And a voltmeter 13 connected to measure a potential difference between the electrode 11 and the second electrode 12.
A lead 14 for connecting to the voltmeter 13 is connected to one end of the first electrode 11 in the longitudinal direction (the end opposite to the side disposed below when immersed in the tap water 20). Yes. The lead 14 is provided with a terminal (not shown) connected to the voltmeter 13 at one end in the longitudinal direction (the end opposite to the side connected to the first electrode 11).
Similarly, the second electrode 12 has a lead 15 for connecting to the voltmeter 13 at one end in the longitudinal direction (the end opposite to the side disposed below when immersed in the tap water 20). It is connected. The lead 15 is provided with a terminal (not shown) connected to the voltmeter 13 at one end in the longitudinal direction (the end opposite to the side connected to the second electrode 12).

The metal constituting the first electrode 11 is more reactive to free residual chlorine in the tap water 20 than the metal constituting the second electrode 12. In this embodiment, the metal which comprises the 1st electrode 11 is highly reactive with respect to the free residual chlorine in the tap water 20 that the metal which comprises the 1st electrode 11 is contained in the tap water 20 (for example, It means that the electrode potential changes by reacting with 1 ppm to 10 ppm of free residual chlorine.
When water is sterilized with a chlorine compound to produce tap water, for example, when chlorine gas is dissolved in water, water (H ₂ O) and chlorine gas (Cl ₂ ) react to produce hypochlorous acid (HOCl). ) And hydrochloric acid (HCl) are generated, and a part of hypochlorous acid (HOCl) is dissociated into hypochlorite ions (OCl ⁻ ) and hydrogen ions (H ⁺ ). In the first electrode 11, a reduction reaction of free residual chlorine (for example, hypochlorite ion (OCl ⁻ )) as shown in the following formula (1) occurs.
OCl ⁻ + H ₂ O + 2e ⁻ → Cl ⁻ + 2OH ⁻ (1)
On the surface of the first electrode 11, a reduction reaction of free residual chlorine as shown in the above formula (1) and an oxidation reaction paired therewith (when the first electrode 11 is a corrosive metal, the following formula (2) The metal (M) dissolution (metal ion (Mn ⁺ ) separation) reaction as shown in FIG. ² occurs, and the reduction reaction and the oxidation reaction are balanced to obtain a steady-state potential.

On the other hand, the metal constituting the second electrode 12 is less reactive to free residual chlorine in the tap water 20 than the metal constituting the first electrode 11. In this embodiment, the metal which comprises the 2nd electrode 12 is low in the reactivity with respect to the free residual chlorine in the tap water 20 that the metal which comprises the 2nd electrode 12 is contained in the tap water 20 (for example, It means that the electrode potential does not change by reacting with 1 ppm to 10 ppm of free residual chlorine. When the second electrode 12 is a corrosive metal, the metal (M) dissolution (separation of metal ions (M ^{n +} )) reaction shown in the following formula (2) and the dissolved oxygen contained in the solution The potential becomes a steady state in a state balanced with the reduction reaction or the hydrogen generation reaction from water.
M → M ^{n +} + ne ⁻ (2)
(However, n is 1 or 2.)

Further, the metal constituting the first electrode 11 and the metal constituting the second electrode 12 approximate the amount of change in electrode potential with respect to the amount of change in the water quality factor and environmental factor of the tap water 20. Here, the water quality factor is a water quality management item that changes the potential of tap water 20 such as pH, dissolved oxygen concentration, chloride ion concentration, hardness components (Ca, Mg), and the like. Further, the environmental factor is an assembly amount that changes a potential such as a temperature of the tap water 20. This indicates that there is the following relationship between the metal constituting the first electrode 11 and the metal constituting the second electrode 12. Here, focusing on the pH of the tap water 20, the relationship between the metal constituting the first electrode 11 and the metal constituting the second electrode 12 will be described.
In a state where the concentration of free residual chlorine in the tap water 20 is constant, only the pH of the tap water 20 is changed, and the electrode potential of the metal constituting the first electrode 11 and the metal potential constituting the second electrode 12 are changed. The electrode potential is measured, and a graph showing the relationship between pH and electrode potential is created for the metal constituting each electrode. For example, with pH as the X axis (horizontal axis) and electrode potential as the Y axis (vertical axis), the relationship between the pH and the electrode potential for each of the metal constituting the first electrode 11 and the metal constituting the second electrode 12 is as follows. Create the graph shown. From the graph, a straight line (linear function) representing the relationship between pH and electrode potential is obtained for each of the metal constituting the first electrode 11 and the metal constituting the second electrode 12. In the present embodiment, the slope of the straight line related to the metal constituting the first electrode 11 and the slope of the straight line related to the metal constituting the second electrode 12 are approximated. In other words, the straight line related to the metal constituting the first electrode 11 and the straight line related to the metal constituting the second electrode 12 are substantially parallel.

Examples of the metal that satisfies the relationship between the first electrode 11 and the second electrode 12 include the following.
As the metal constituting the first electrode 11, platinum or titanium is preferable because the change in the electrode potential with time is small and the reactivity with a small amount of free residual chlorine contained in the tap water 20 is high.
The metal constituting the second electrode 12 is preferably a metal that can form a strong passive film in a neutral solution. Examples of such a metal include SUS316, SUS316L, tungsten (W), tantalum (Ta), and the like. Among these, SUS316 or SUS316L is preferable because the change in electrode potential with time is small.

  The solid-type residual chlorine sensor 10 of this embodiment is provided and used for piping (water pipe) 30 as shown in FIG. 2, for example. That is, the first electrode 11 is provided to the pipe 30 so that the first electrode 11 is inserted into the through hole 31 that penetrates the pipe 30 in the thickness direction, and the first electrode 11 is exposed to the inner surface 30 a of the pipe 30. It is done. In addition, that the 1st electrode 11 is exposed to the inner surface 30a of the piping 30 is that the front-end | tip 11a of the 1st electrode 11 is arrange | positioned on the substantially same surface as the inner surface 30a of the piping 30, in other words, the 1st electrode. 11 is arranged so that the tip 11a of 11 does not protrude from the inner surface 30a of the pipe 30 into the pipe 30. Similarly, the second electrode 12 is inserted into the through-hole 32 that penetrates the pipe 30 in the thickness direction, and the second electrode 12 is connected to the pipe 30 so that the second electrode 12 is exposed to the inner surface 30a of the pipe 30. Provided. In addition, that the 2nd electrode 12 is exposed to the inner surface 30a of the piping 30 is that the front-end | tip 12a of the 2nd electrode 12 is arrange | positioned substantially on the same surface as the inner surface 30a of the piping 30, in other words, the 2nd electrode. That is, the 12 tips 12 a are arranged so as not to protrude into the pipe 30 from the inner surface 30 a of the pipe 30.

  Thus, the first electrode 11 and the second electrode 12 are provided so as to be exposed to the inner surface 30a of the pipe 30 without protruding from the inner surface 30a of the pipe 30 into the pipe 30. The second electrode 12 is less affected by the flow velocity of the tap water 20 flowing in the pipe 30 and suppresses the occurrence of pressure loss.

The portions of the first electrode 11 and the second electrode 12 that are in contact with the tap water 20, that is, the tip 11 a of the first electrode 11 and the tip 12 a of the second electrode 12 are preferably surrounded by the porous body 40.
The shape of the porous body 40 is not particularly limited. For example, the shape of the porous body 40 is preferably along the shape of the tip 11 a of the first electrode 11 and the tip 12 a of the second electrode 12.

The porous body 40 is not particularly limited, and examples thereof include porous ceramics having continuous pores (holes).
The porosity of the porous body 40 is not particularly limited, but at least the first electrode 11 and the second electrode 12 are always in contact with the tap water 20 and do not greatly disturb the flow of the tap water 20 flowing in the pipe 30. It needs to be about.

  As described above, the portions of the first electrode 11 and the second electrode 12 that are in contact with the tap water 20 are surrounded by the porous body 40, thereby reducing the influence of the flow velocity of the tap water 20 flowing in the pipe 30. With the 1 electrode 11 and the 2nd electrode 12, the density | concentration of the free residual chlorine in the tap water 20 can be measured more correctly.

  The solid-type residual chlorine sensor 10 causes the first electrode 11 and the second electrode 12 to come into contact with the tap water 20, so that a small amount of free residual chlorine contained in the tap water 20 causes the first electrode 11 to The balance between the reduction reaction of free residual chlorine and the oxidation reaction on the metal (M) occurs, and the balance condition changes according to the concentration of free residual chlorine, so that the potential difference between the first electrode 11 and the second electrode 12 Changes. Further, since the potential difference between the first electrode 11 and the second electrode 12 is proportional to the concentration of free residual chlorine contained in the tap water 20, the concentration of free residual chlorine can be measured from the potential difference.

  According to the solid-type residual chlorine sensor 10 of the present embodiment, the simple structure of the first electrode 11, the second electrode 12 and the voltmeter 13 is free from maintenance in the tap water 20 in the middle of the pipe 30 for a long time without maintenance. The concentration of residual chlorine can always be measured. That is, unlike the absorptiometry, it is not necessary to use a coloring reagent, so that the concentration of free residual chlorine in tap water can be measured at low cost.

(2) Second Embodiment FIG. 3 is a schematic perspective view showing a second embodiment of the solid-type residual chlorine sensor of the present invention.
The solid-type residual chlorine sensor 50 of this embodiment is used for measuring the concentration of free residual chlorine in tap water, and includes a first electrode 51 serving as a cathode, a second electrode 52 serving as an anode, and a first electrode 51. And a voltmeter 53 connected to the second electrode 52.
The first electrode 51 and the second electrode 52 have a similar shape to the pipe 60 so as to form part of the pipe (water pipe) 60 in which the solid-type residual chlorine sensor 50 is provided. As shown in FIG. 3, for example, when the pipe 60 is cylindrical, the first electrode 51 and the second electrode 52 have an annular shape, and the inner diameter and outer diameter thereof are equal to the inner diameter and outer diameter of the pipe 60. ing. Further, an insulating member 56 is provided between the first electrode 51 and the second electrode 52 to prevent these two electrodes from being short-circuited. The insulating member 56 has a shape similar to that of the first electrode 51 and the second electrode 52, and has an annular shape in the present embodiment.

  The inner surface 51 a of the first electrode 51, the inner surface 52 a of the second electrode 52, and the inner surface 56 a of the insulating member 56 form the same surface as the inner surface 60 a of the pipe 60. Further, the outer surface 51 b of the first electrode 51, the outer surface 52 b of the second electrode 52, and the outer surface 56 b of the insulating member 56 form the same surface as the outer surface 60 b of the pipe 60.

The lead 54 for connecting with the voltmeter 53 is connected to the outer surface 51b of the first electrode 51. The lead 54 has a terminal (not shown) connected to the voltmeter 53 at one end in the longitudinal direction (the end opposite to the side connected to the first electrode 51).
Similarly, a lead 55 for connecting to the voltmeter 53 is connected to the outer surface 52b of the second electrode 52. The lead 55 is provided with a terminal (not shown) connected to the voltmeter 53 at one end in the longitudinal direction (the end opposite to the side connected to the second electrode 52).

  The first electrode 51 is configured in the same manner as the first electrode 11 of the first embodiment described above. The second electrode 52 is configured similarly to the second electrode 12 of the first embodiment described above.

  In the solid-type residual chlorine sensor 50 of the present embodiment, the first electrode 51 and the second electrode 52 form a part of the pipe 60, so that the first electrode 51 and the second electrode 52 are connected to the inner surface 60a of the pipe 60. It is provided so as to be exposed to the inner surface 60a side of the pipe 60 without protruding into the pipe 60, and the first electrode 51 and the second electrode 52 reduce the influence of the flow rate of tap water flowing in the pipe 60, The first electrode 51 and the second electrode 52 can measure the concentration of free residual chlorine in tap water more accurately.

[Water meter]
The water meter of this embodiment is provided with the solid-type residual chlorine sensor of the above-mentioned embodiment.
Although the form of the water meter of this embodiment is not particularly limited, the indicator rotating water meter, dry water meter, vertical shaft impeller water meter, turbine water meter, electronic water meter, contact pulse output Water meter, electromagnetic water meter, etc.

  The water meter of the present embodiment is, for example, one in which the solid-type residual chlorine sensor of the above-described embodiment is provided on the measurement pipe of the water meter. That is, the solid residual chlorine sensor of the above-described embodiment is provided in a portion where tap water flows in the water meter (portion for measuring the flow rate of tap water).

  According to the water meter of this embodiment, not only the flow rate of tap water but also the concentration of free residual chlorine in tap water can always be measured at a position closer to the faucet (faucet), and the indicator value of the water meter The influence of the flow rate can be corrected based on the change with time.

  Hereinafter, the present invention will be described more specifically with experimental examples, but the present invention is not limited to the following experimental examples.

"Experiment 1"
A 0.02M phosphate buffer solution containing sodium monohydrogen phosphate and sodium dihydrogen phosphate in a molar ratio of 1: 1 was prepared and used as a base solution.
An aqueous solution containing free residual chlorine was injected into this base solution to prepare a hypochlorous acid solution having a hypochlorous acid concentration of 0.1 ppm.
An Ag / AgCl electrode was prepared as a reference electrode.
An electrode made of platinum was prepared as a working electrode, the surface was polished with silicon carbide (SiC) No. 2400 polishing paper, and then degreased with ethanol.
These reference electrode and working electrode were connected to a voltmeter.
Next, the reference electrode and the working electrode were immersed in the base solution injected into the flow cell, and the base solution was circulated at room temperature for 60 minutes to stabilize the working electrode potential.
Next, as the solution to be circulated in the flow cell, the base solution and the hypochlorous acid solution were alternately switched, and the potential of the working electrode was measured. The results are shown in FIG.
From the results of FIG. 4, it was confirmed that the potential of the working electrode repeatedly changed from the start (on) to the end (off) of the flow of the hypochlorous acid solution. That is, the potential of the electrode made of platinum (Pt) changed greatly depending on the hypochlorous acid solution contained in the solution, and a reproducible response could be obtained.

"Experimental example 2"
In the same manner as in Experimental Example 1, a base solution and a hypochlorous acid solution were prepared, and a reference electrode was prepared.
An electrode made of SUS316 was prepared as a working electrode, and the surface was polished with silicon carbide (SiC) No. 2400 polishing paper, and then degreased with ethanol.
These reference electrode and working electrode were connected to a voltmeter.
Subsequently, the potential of the working electrode was measured in the same manner as in Experimental Example 1. The results are shown in FIG.
From the results of FIG. 5, it was confirmed that the potential of the working electrode repeatedly changed from the start (on) to the end (off) of the flow of the hypochlorous acid solution. That is, the potential of the electrode made of SUS316 changes depending on the hypochlorous acid solution contained in the solution, although the amount of change in potential of platinum according to the residual chlorine concentration is smaller.

"Experiment 3"
In the same manner as in Experimental Example 1, a base solution and a hypochlorous acid solution were prepared, and a reference electrode was prepared.
An electrode made of SUS316L was prepared as a working electrode, and the surface was polished with silicon carbide (SiC) No. 2400 polishing paper, and then degreased with ethanol.
These reference electrode and working electrode were connected to a voltmeter.
Subsequently, the potential of the working electrode was measured in the same manner as in Experimental Example 1. The results are shown in FIG.
From the results of FIG. 6, it was confirmed that the potential of the working electrode repeatedly changed from the start (on) to the end (off) of the flow of the hypochlorous acid solution. That is, the potential of the electrode made of SUS316L changes depending on the hypochlorous acid solution contained in the solution, although the amount of change in potential of platinum according to the residual chlorine concentration is smaller.

"Experimental example 4"
Using a pH buffer solution, a test solution (A-3) having a pH of 4, a test solution (B-3) having a pH of 7, a test solution having a pH of 8.4 (C-3), and a pH of 9. 3 test solution (D-3) was prepared.
A reference electrode was prepared in the same manner as in Experimental Example 1.
Similar to Experimental Example 1, an electrode made of platinum (Pt) was prepared as a working electrode. Further, as in Experimental Example 2, an electrode made of SUS316 was prepared as a working electrode. Further, as in Experimental Example 3, an electrode made of SUS316L was prepared as a working electrode.
Each working electrode and reference electrode were connected to a voltmeter.
Next, the reference electrode and the working electrode were immersed in the base solution injected into the flow cell, and the base solution was circulated at room temperature for 60 minutes to stabilize the working electrode potential.
Next, in the flow cell, the test solutions (A-3), (B-3), (C-3), and (D-3) were allowed to flow in order for 5 minutes, and each test solution was flowing. The potential of the working electrode was measured. The results are shown in FIG.
From the results of FIG. 7, it was confirmed that the potential of any working electrode was proportional to the pH of the test solution. Also, the change in potential of the electrode made of platinum (Pt) with respect to the change in pH of the test solution, the change in potential of the electrode made of SUS316 with respect to the change in pH of the test solution, and the change in pH of the test solution. The amount of change in potential of the electrode made of SUS316L is similar to each other.

“Experimental Example 5”
A base solution was prepared in the same manner as in Experimental Example 1.
In the same manner as in Experimental Example 1, a free residual chlorine solution was prepared.
An electrode made of platinum (Pt) was prepared and degreased with ethanol.
An electrode made of SUS316L was prepared and degreased with ethanol.
These two electrodes were connected to a voltmeter.
Next, the two electrodes were immersed in the base solution injected into the flow cell, and the base solution was allowed to flow at room temperature for 60 minutes to stabilize the potential of the two electrodes.
Next, as a solution to be circulated in the flow cell, the base solution and the free residual chlorine solution were alternately switched to measure the potential difference. The results are shown in FIG.
From the result of FIG. 8, it was confirmed that the potential difference repeatedly changed from the start (on) to the end (off) of the flow of the free residual chlorine solution. That is, the potential difference between the electrode made of platinum (Pt) and the electrode made of SUS316L varies depending on a trace amount (1 ppm) of free residual chlorine contained in the solution.

10, 50 ... solid type residual chlorine sensor, 11, 51 ... first electrode, 12, 52 ... second electrode, 13, 53 ... voltmeter, 14, 15, 54, 55 ... -Reed, 20 ... tap water, 30, 60 ... piping, 31, 32 ... through-hole, 40 ... porous body, 56 ... insulating member.

Claims (6)

A first electrode; a second electrode; and a voltmeter connected to the first electrode and the second electrode;
The metal constituting the first electrode is more reactive to free residual chlorine in tap water than the metal constituting the second electrode,
The metal constituting the first electrode and the metal constituting the second electrode are solids characterized in that the amount of change in electrode potential approximates the amount of change in the water quality factor and environmental factor of the tap water Mold residual chlorine sensor.   The metal constituting the first electrode is platinum or titanium, and the metal constituting the second electrode is a metal capable of forming a strong passive film in a solution near neutrality. The solid-type residual chlorine sensor according to claim 1.   The solid-type residual chlorine sensor according to claim 1 or 2, wherein the pair of electrodes are provided so as to be exposed on an inner surface of a pipe through which the tap water flows.   The solid residual chlorine sensor according to claim 3, wherein the pair of electrodes form part of the pipe.   4. The solid-type residual chlorine sensor according to claim 1, wherein portions of the pair of electrodes that are in contact with the tap water are surrounded by a porous body.   A water meter comprising the solid-type residual chlorine sensor according to any one of claims 1 to 5.

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