JPS628050A - Method and apparatus for measuring concentration of oxidizable substance in liquid to be inspected - Google Patents

Abstract

PURPOSE:To effectively remove contamination adhered to the surface of a measuring positive pole during measurement, by immersing the measuring positive pole, a measuring negative pole and an electrolytic polishing electrode in a liquid to be inspected and constituting a galvanic cell of the positive pole, the negative pole and the liquid to be inspected. CONSTITUTION:A measuring positive pole 2, a measuring negative pole 1 and an electrolytic polishing electrode 3 are immersed in a liquid 4 to be inspected. At this time, a galvanic cell is formed of the positive pole 2, the negative pole 1 and the liquid 4 to be inspected and the positive pole 2 and the negative pole 1 are connected to an ammeter 5 to measure a current value. Because this current value is proportional to the concn. of an oxidizable substance, said concn. can be calculated. After the measurement of concn. for a predetermined time, the position of a change-over switch SW is changed over from AB to AC. Whereupon, the positive pole 2 is connected to the electrolytic electrode 3 through a power source 6 and the electrolytic polishing on the surface of the positive pole 2 is performed to remove scale. After a predetermined time, if the position of the switch SW is changed over from AC to AB, electrolytic polishing is finished and measurement is again continued.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for measuring the concentration of oxidizing substances in a test liquid and a rounding device for carrying out this method, and particularly relates to a method for measuring the concentration of oxidizing substances in a test liquid, and in particular to a method for measuring the concentration of oxidizing substances in a test liquid. The present invention relates to a measuring method for determining the concentration of an oxidizing substance by making use of the fact that the current flowing between the galvanic cells is proportional to the concentration of the oxidizing substance, and the apparatus used to carry out the method.

Conventional technology The conventional method for measuring the concentration of oxidizing substances such as hypochlorous acid in a test solution consists of immersing a positive electrode and a negative electrode in the test solution to form a galvanic cell. This method measures the current value, which changes in proportion to the concentration of a substance.

Problems to be Solved by the Invention When a platinum electrode is used as the positive electrode and a silver electrode is used as the negative electrode in this galvanic cell, a film is formed on the platinum electrode side due to contamination, resulting in a decrease in output. The only way to recover from this decline is to polish the electrode with a cloth or the like. With such a cleaning method, complete recovery cannot be expected, and the output will soon drop again. Therefore, measurement errors become large and automatic measurement over a long period of time is difficult.

An object of the present invention is to provide a concentration measuring method and apparatus that solve the above-mentioned problems.

Means for solving the problems, that is, the present invention is as follows: By configuring a galvanic cell and connecting the positive and negative electrodes to an ammeter, the current value flowing through the ammeter is measured. Measure the concentration, and after measuring for a predetermined time, disconnect the positive electrode and the ammeter 9, connect the positive electrode to the electrolytic polishing electrode via a DC power supply, and apply electricity for a predetermined time using the electrolytic polishing electrode as the positive electrode. By doing so, electrolytic polishing is performed to remove the film formed on the surface of the positive electrode during measurement, and then the connection between the positive electrode and the DC power source is cut off, and the measurement is performed by connecting the positive electrode and the ammeter again. The above problem was solved by providing a method for measuring the concentration of oxidizing substances in a test liquid.

Furthermore, the present invention also provides an apparatus for carrying out the above measurement method. That is, the present invention provides (2) "an elongated hollow rod-like body made of synthetic resin; A negative electrode for measurement, a positive electrode for measurement, an electrode for electrolytic polishing,
The hollow part is energized, and the first conductor wire is connected to the negative electrode for measurement and the other end is connected to the first terminal of the ammeter, and one end is connected to the positive electrode for measurement and the other end is connected to the ammeter via a switch. oxidizing substances in the test liquid, consisting of a second conductive wire connected to the second terminal of Concentration measuring device. "I will provide a.

DESCRIPTION OF PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing the principle of the measuring method and apparatus of the present invention. In FIG. 1, a test liquid 4 containing an oxidizing substance such as hypochlorous acid is contained in a tank 7, and a measuring positive electrode 2 (preferably made of platinum) is contained in the test liquid 4. The measurement negative electrode 1 (preferably made of silver) and the electropolishing electrode 3 (preferably made of platinum) are immersed. Then,
A galvanic cell is formed by the positive electrode 2, the negative electrode 1, and the test liquid 4, so when the positive electrode 2 and the negative electrode 1 are connected to the ammeter 5, a current flows, and the current value displayed on the ammeter is the value of the current in the test liquid. Since it is proportional to the concentration of the oxidizing substance, the concentration can be determined from the current value.

The current during measurement is as shown by the arrow (→), positive electrode 2 → A →
B → terminal E2 → ammeter 5 → terminal E1 → negative electrode 1.

If this measurement is continued, metal ions will precipitate on the surface of the positive electrode 2, and scale will adhere to the positive electrode.

Therefore, the catalytic action of platinum at the positive electrode is inhibited over time.

On the other hand, in negative electrode 1, silver is ionized and always in an active state, so
Unlike the positive electrode, there is no scale adhesion.

When this measurement is continued, metal ions are deposited on the surface of the positive electrode 2 and become in an oxidized state, and the negative electrode 1 becomes in a cyclic state. Therefore, the positive electrode side tends to accumulate scale and become dirty, so it is necessary to remove the dirt in order to restore the performance of the positive electrode. For this purpose, the following electropolishing method is used in the present invention.

That is, after measuring the concentration for a predetermined period of time, the position of the changeover switch SW shown in FIG. 1 is changed from the AB position to the AC position.

Then, the connection between the positive electrode 2 and the ammeter 5 is cut off, and the positive electrode 2
is connected to the electrolytic polishing electrode 3 via a DC power source 6 (preferably a battery), and the current flows to the electrode 3 as shown by the arrow.
- Flows from DC power supply 6 → C → A → positive electrode 2, electrolytic polishing of the positive electrode surface is performed, scale is removed, and the measurement performance is 10
Recovers 0%. In this case, the electrolytic polishing electrode 3 is used as a positive electrode. After electrolytic polishing for a predetermined time, the switch 5Wt-
When the AB position is switched from the AC position, the electrolytic polishing ends and the measurement is continued again.

Switch SW position from AB to AC and from AC to A
Switching to B can be done automatically, especially when
Preferably, this is done using a 4 hour timer. for example,
By using a 4-volt battery as a DC power source and performing electrolytic polishing once a day for 30 minutes, concentration measurements can be continued without any human intervention.

The apparatus for carrying out the above-mentioned measuring method of the present invention includes the first
The device shown in the figure may be used, but the positive electrode 2 in Figure 1 and the conductor? , terminal E2, negative electrode 1, conductor 8, terminal E1, electrode 3, conductor 10 are advantageously used in one assembly. FIG. 2 shows such an assembly. That is, a long and thin hanging rod-shaped body 11 made of synthetic resin, and negative electrodes 1' for measurement held by the rod-shaped bodies so as to be exposed on the surface of the rod-shaped body at intervals in the axial direction of the rod-shaped body. It has a positive electrode 2 for measurement and an electrode 3' for electrolytic polishing. FIG. 5 shows a longitudinal cross-sectional view of the electrode assembly of FIG. 2. The measurement negative electrode 1' may be a silver plate wrapped around the outer circumference of a synthetic resin rod-shaped body 11 and fixed thereto, but preferably a silver rod-shaped body having a hollow part 15 communicating with the hollow part 12 of the synthetic resin rod-shaped body. 1', and screws 14 and 15 are preferably formed at both ends in the axial direction of the silver rod-shaped body 1'. It is preferable to form a female thread corresponding to the male thread 14.15 in the synthetic resin rod-like body, and to fix the silver rod-like body 1' to the synthetic resin rod-like body 11 by engaging the female thread with the male thread 14.15. With this configuration, it is possible to lengthen the time it takes for the negative electrode 1' to elute and reach the end of its life.

The positive electrode 2' for measurement and the electrode 3' for electrolytic polishing are preferably made of platinum.Since platinum is expensive, in order to obtain the same surface area with a minimum volume, a thin platinum wire is used, and this is made into a synthetic resin rod shape. It is preferable to wrap it around the surface of the body 11.

As shown in FIGS. 2 and 3, the positive electrode 2' is preferably positioned intermediate the negative electrode 1' and the electrode 3' when viewed in the axial direction of the rod-shaped body. The reason for this is that electrode 3' does not exist in the path of the current that can pass through the test liquid between positive electrode 2' and negative electrode 1' during measurement, and that electrode 3' does not exist in the path of the current that can pass through the test liquid between positive electrode 2' and negative electrode 1' during electropolishing.
This is because the negative electrode 1' does not exist in the path of the current flowing in the test liquid between the two and does not get in the way.

Example of action (a) Flow of electricity during measurement Positive electrode (platinum electrode): 2 HOd, + 4 e −+ 2 HCfl +
2 (0) M++e -1 → M...Metal is precipitated and attached to the positive electrode.Metal ions in the solution are deposited on the negative electrode (silver electrode): 4Ag→4Ag+4e-...Silver is ionized and in an active state (mouth) Electricity flow during cleaning (electrolytic polishing) Positive electrode (platinum electrode): M→M”+e-...Electrode (platinum electrode) where the attached 9M is dissolved and the polar metal ions are cleaned: M + e- M Example In a swimming pool, a bypass circuit was provided between the suction side and the discharge side of the pump of the pool circulation system, and the device of the present invention was placed in the bypass circuit, and the residual chlorine concentration was measured.

FIG. 4 is a graph showing the measurement results.

The horizontal axis is the time (24 hour system), and the vertical axis is the residual chlorine concentration (pp.
m).

The residual chlorine concentration can be determined by reading the value of the current flowing between the positive and negative electrodes with an ammeter and calculating the concentration proportional to the current value, but it is better to have a concentration scale on the ammeter. It's convenient.

The concentration value displayed on the recording meter using the electrode of the present invention is called "1 indicated value", and the value measured by the orthotolidine colorimeter of residual chlorine in the liquid to be measured is called "1 measured value". I'll decide.

In FIG. 4, between the solid line A and B is the indicated value=measured value. When electrolytic polishing is performed by applying a DC voltage of 4 volts between the positive electrode and the electrode for 30 minutes starting from 24:00, the indicated value suddenly rises to C (concentration around 1.0), and then for about 2 hours 30 minutes.
The indicated value decreases for minutes and changes along solid lines C and D.

The single-dot chain @B-D indicates the measured value, so the indicated value of C→D and the measured values of B and D do not match.

However, since this electrolytic polishing is carried out around 24:00 in the middle of the night when there is little variation in water quality, this period can be ignored to some extent. The solid line D→E indicates the indicated value=measured value. If electrolytic polishing is not performed, the indicated value will be curve B- as shown by the broken line.
FG, and a difference or error appears between the measured value and the indicated value.

Effects of the Invention Since the present invention has the above-described structure and operation, dirt adhering to the surface of the positive electrode for measurement during measurement can be effectively removed by applying a DC voltage between the positive electrode and the electrode. It is possible to recover 100% of the measurement performance between the measurement electrodes, and there is no error seen in the prior art.

Further, by automatically switching the cycle between electrolytic polishing and measurement using a timer, continuous operation for a long time is possible.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the principle of the measuring method of the present invention. FIG. 2 is an elevational side view of one embodiment of the electrode assembly of the present invention. FIG. 3 is a longitudinal sectional view of FIG. 2. FIG. 4 is a graph showing the results measured using the method of the present invention. 2.2′・・・・・・・・・Positive electrode for measurement 1.1・
......Negative electrode for measurement 3.3...
... Electrolytic polishing electrode 8, 9.10... Conductor wire El, E2... Terminal

Claims (1)

[Scope of Claims] 1. A positive electrode for measurement, a negative electrode for measurement, and an electrode for electrolytic polishing are immersed in a test liquid, a galvanic cell is constituted by the positive electrode, a negative electrode, and the test liquid, and the positive electrode and the negative electrode are By connecting to an ammeter, the value of the current flowing through the ammeter is measured, and the concentration is measured using the fact that the current value is proportional to the concentration of the oxidizing substance in the test liquid. After that, the positive electrode is disconnected from the ammeter, the positive electrode is connected to the electrolytic polishing electrode via a DC power supply, and the electrolytic polishing electrode is used as the positive electrode and current is applied for a predetermined period of time to prevent formation on the positive electrode surface during measurement. The concentration of oxidizing substances in the test liquid is measured by electropolishing to remove the coated film, then disconnecting the positive electrode from the DC power source, and then connecting the positive electrode to the ammeter again. Measuring method. 2. The method for measuring the concentration of an oxidizing substance according to claim 1, characterized in that switching between concentration measurement and electrolytic polishing is performed using a timer. 3. The concentration measuring method according to claim 1 or 2, wherein the DC power source is a battery. 4. The method according to claim 1, wherein the oxidizing substance is hypochlorous acid. 5. An elongated hollow rod-shaped body made of synthetic resin, and a negative electrode for measurement and a positive electrode for measurement held by the rod-shaped body so as to be exposed on the surface of the rod-shaped body at intervals in the axial direction of the rod-shaped body. An electrolytic polishing electrode, a first conductor that passes through the hollow part and connects one end to the negative electrode for measurement and the other end to the first terminal of the ammeter, and one end to the positive electrode for measurement and the other end to the switching device. in the test liquid, consisting of a second conductor connected to the second terminal of the ammeter via the 2nd conductor, and a third conductor connected to the electrolytic polishing electrode at one end and provided with a switching terminal at the other end via a DC power supply. A device for measuring the concentration of oxidizing substances. 6. The negative electrode for measurement is a silver rod-shaped body having a hollow part communicating with the hollow part of the synthetic resin rod-shaped body, and the silver rod-shaped body has a male thread at both ends in the axial direction, and a female thread corresponding to the male thread is synthesized. 6. The concentration measuring device according to claim 5, wherein the silver rod is formed into a resin rod and is fixed to the synthetic resin rod by engaging a male thread and a female thread. 7. The concentration measuring device according to claim 5 or 6, wherein the measuring positive electrode and the electrolytic polishing electrode are made of a platinum wire wound around the outer periphery of a synthetic resin rod. 8. The concentration measuring device according to claim 5, wherein the measuring positive electrode is positioned between the measuring negative electrode and the electrolytic polishing electrode when viewed in the axial direction of the synthetic resin rod. 9. The concentration measuring device according to claim 5, wherein the synthetic resin rod is made of vinyl chloride resin.