JP2000131276A - Potable type residual chlorine meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a portable type residual chlorine meter of simple constitution, operatable easily to be handled without requiring any skill, and capable of measuring automatically residual chlorine with high precision. SOLUTION: This meter comprises an instrument main body 1 having a signal processing and controlling part, a power source circuit part and a display part 4, and a detecting part 2 connected to the main body 1 via a connecting cable 3. The detecting part 2 is constituted of a test liquid collecting cup 6 and an electrode supporting cap 7 engaged disengageably with the cup 6, and the electrode supporting cap 7 is provided with a reference electrode 8 dipped into a sample liquid inside the cup 6 and a sensing electrode 9. The reference electrode 8 is constituted by suspending into an electrode tube filled with an electrolyte a metal wire with a metal coating film applied only in a portion contacting with the electrolyte.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a portable residual chlorine analyzer,
More specifically, it relates to a portable residual chlorine meter that can easily and accurately measure the residual amount of chlorine injected into tap water, pool water, industrial water, etc. for the purpose of sterilization or sewage treatment. It is.

[0002] The residual chlorine is chlorine added for disinfecting water, and the added chlorine is dissolved in water and is ionized depending on the temperature and pH of the water. When chlorine dissolves in water, it reacts with water to form hypochlorous acid (HOCl) and hydrochloric acid, and a part of hypochlorous acid dissociates into hypochlorite ion (OCl-) and hydrogen ion. . This hypochlorous acid is generally called residual chlorine (free residual chlorine).

[0003]

2. Description of the Related Art Conventionally, several types of products have been sold as residual chlorine analyzers. The measurement principles of these devices can be roughly classified into the following two types. 1) A method in which the concentration is determined based on the degree of color of a liquid chemically reacted using a reagent product. 2) A method of determining the concentration by converting the degree of dissolved gas or ions of a liquid into an electric signal.

[0004] In Japan, a method for measuring a dye reaction using a reagent product of 1) is widely used. Although the measuring device of the method 2) is also used, since this type has many large machines and is of an installation type, it is limited to use in a specific place. Although there are portable devices of the type 2), they are not widely used due to their high cost.

[0005] Both methods will be described in more detail. In a residual chlorine analyzer of the type using a reagent product of 1), ortho-tolidine is used as a reagent. In this method, when free residual chlorine or bound residual chlorine is present in water, O-
Trizine is oxidized by chlorine to form yellow holoquinone, which exhibits a color reaction. At that time, free residual chlorine and O-tolidine react instantaneously, but it takes several minutes for combined residual chlorine and O-tolidine to react. Therefore, in this method,
It is possible to measure two chlorines separately.

The ortho-tolidine method has the advantages that the amount of the sample solution may be small, the operation is simple and the initial cost is low, but the running cost is high, and carcinogenic and toxic substances are used. Therefore, careful handling is required, and 6
There is a problem in safety, such as chromium (VI) is also toxic.

[0007] Further, in the case of colorimetry by visual observation, there is a problem in terms of accuracy due to differences in individuals, differences in absorption wavelength between a standard colorimetric solution and a colored sample solution, and differences in coloration degree depending on temperature. is there. Furthermore, there is also a disadvantage that the measurement becomes impossible if the sample liquid is turbid or colored.

The above method 2) is generally called an electrode method, and the method for measuring the residual chlorine concentration is based on amperometry (current measuring method). Amperometry is a technique in which one indicator electrode (electrode having a surface on which the desired electrochemical phenomenon occurs) and one reference electrode (electrode having a known potential regardless of the intensity of the passing current) are immersed in a solution. A method of applying an appropriately selected constant voltage between the two electrodes, and sometimes using the zero applied voltage method by short-circuiting the two electrodes. When an electrolyte is present in the solution, the chemical energy released by the electrolysis is converted to an electric current. This current is a function of the concentration and potential of the electrically active substance. Therefore, under certain conditions, the concentration of the substance can be obtained from the current value.

In this electrode method, the buffer solution and the electrode treatment solution used are less toxic than the ortho-tolidine method, and are of the meter type or digital type. 5 ° C due to temperature compensation
There is an advantage that accurate measurement can be performed even with a sample solution up to 30 ° C., and that the sample solution is not affected by turbidity or color of the sample solution. However, on the other hand, there is a disadvantage that the operation is complicated and requires skill.

[0010] In the case of a diaphragm electrode using a diaphragm for the detection electrode and the comparison electrode, skill is required in cleaning the electrode and replacing the diaphragm when the diaphragm is soiled, and replenishing the electrolyte when the electrolyte has disappeared. It costs. On the other hand, in the case of the exposed electrode in which the detection electrode and the comparison electrode are in direct contact with the sample liquid, the comparative electrode is heavily soiled, so that the frequency of polishing and replacement of the comparison electrode increases, and the cost increases.

[0011]

As described above, the conventional apparatus for measuring residual chlorine has many drawbacks. Therefore, the present invention has no such drawbacks. It is an object of the present invention to provide a portable residual chlorine meter which can be easily handled without skill and can measure residual chlorine automatically and accurately.

[0012]

SUMMARY OF THE INVENTION The present invention comprises an instrument body having a signal processing and control circuit section, a power supply circuit section, and a display section, and a detecting section connected to the instrument body via a connection cable. The detection unit is composed of a sample collection cup and an electrode support cap that is removably fitted to the cup,
The electrode support cap includes a comparison electrode and a detection electrode that are immersed in the sample solution in the test solution collection cup, and the comparison electrode has a metal film only on a portion that comes into contact with the electrolyte in an electrode tube filled with the electrolyte. The above problem has been solved by a portable residual chlorine meter characterized in that the applied metal wire is suspended.

In a preferred embodiment, the metal film of the reference electrode is silver-silver chloride, and the metal wire is a silver wire. Further, a microporous ceramic is loaded on the bottom of the electrode tube of the comparative electrode. Further, a stirring assembly that is immersed in the sample solution in the test solution collection cup is installed on the electrode support cap.

[0014]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a perspective view of a residual chlorine meter according to the present invention. The present residual chlorine meter comprises an instrument body 1 and a casing.
And a detection unit 2 connected via the cable 3. A digital display unit 4 and a switch 5 are provided on the front side of the instrument main body 1, and a battery-powered power supply circuit unit 31 and a signal processing and control circuit unit 32 are built in.

The detecting section 2 includes a test solution collection cup 6 and an electrode support cap 7 which is removably fitted thereto. A reference electrode 8, a detection electrode 9, and an electrode support plug 10 that supports the stirring assembly 23 are fitted to the electrode support cap 7 (see FIG. 2). The support plug 10 has an upper half fitted into the electrode support cap 7 and a lower half fitted into the test solution collection cup 6. A seal ring 11 is provided in the lower half part to be fitted into the test solution collection cup 6, and the sealed state inside the test solution collection cup 6 is maintained. Therefore, scattering of residual chlorine in the sample liquid is prevented, and highly accurate and reliable measurement can be performed.

Many conventional reference electrodes are of the type in which a silver wire is inserted into the electrolyte. However, this method requires a very long time until the electrode can be used as a reference electrode, and the production time and production cost are problematic. Become. In addition, there was a drift of zero potential during use as a reference electrode, and there was also a problem in stability. In order to solve these problems, in the present invention, a method of performing a surface treatment on a silver wire used as a reference electrode is employed, thereby shortening a manufacturing period, reducing manufacturing costs, improving performance, and the like. It was realized.

That is, the comparative electrode 8 of the present invention is of an easily replaceable cassette type, and is preferably provided in an electrode tube 12 made of vinyl chloride or the like filled with an electrolytic solution 13 which is a gel type potassium chloride. A silver wire 15 having a coating 14 of a metal, in particular silver-silver chloride, deposited only on the portion that contacts
Hang a metal wire such as. The silver silver chloride referred to here is, for example, a powder obtained by mixing a silver chloride powder and a silver sulfide powder at a ratio of 10: 1, and is attached to the silver wire 15.

By thus depositing the silver-silver chloride film 14 only on the portion where the silver wire 15 comes into contact with the electrolyte 13, the time from immediately after production to when it can be used as a reference electrode is reduced. It is possible to greatly improve the production efficiency and reduce the production cost. Furthermore, stability was improved.

A connection terminal 16 is detachably fitted into the head of the electrode tube 12 so as to be electrically connected to the end of the silver wire 15. Further, a microporous ceramic 17 is loaded on the bottom of the electrode tube 12. Microporous ceramics 1
No. 7, for example, has a fine pore diameter of 0.2 μm and a water absorption of 15%. By providing such characteristics, it has characteristics substantially equal to those of the conventional diaphragm, and it is possible to minimize volatilization of the electrolyte 13. In addition, the reaction time can be set to the same performance as that of the diaphragm.

The detection electrode 9 is formed by attaching a metal detection electrode 21 made of platinum or the like integrated with a temperature sensor 20 for temperature correction to the bottom of a hollow shaft 19. The detection electrode 9 can improve the measurement error due to the temperature change of the sample liquid by detecting the temperature change when the detection electrode 21 comes into contact with the sample liquid without delay.

Generally, the electrode support plug 10 is further provided with a stirring assembly 23 for stirring the sample liquid. The stirring assembly 23 comprises a stirring shaft 24 provided with a stirring blade 25 at a lower portion and a rotary bearing hole 26 at the upper end for inserting a rotary shaft of a motor 27.

It is well known that the concentration of free residual chlorine is greatly affected by the water peak (hydrogen ion concentration). When the measurement is performed by the electrode method, it is desirable that the measurement be performed with this peak constant. Therefore, in the present invention, preferably, means for supplying a small amount of the buffer solution to the sample solution is provided in the stirring assembly 23.

As means for this purpose, for example, a stirring shaft 24 having a bottomed cylindrical shape is filled with a buffer buffer 28, and the buffer 28 is stirred by centrifugal force accompanying rotation of the stirring shaft 24. Capillary tube arranged at the bottom of shaft 24
A method of dispensing from the outlet 29 by means of a nozzle or a fine hole can be considered.

In this case, in order to achieve a smooth supply, the centrifugal force and the rotating force accompanying the rotation of the stirring shaft 24 are used.
It is preferable that the air pressure in the stirring shaft 24 be increased. To this end, an air hole 30 for obtaining an increase in air pressure due to rotation is provided above the stirring shaft 24.
(See FIG. 4). By doing so, the outside of the air hole 30 plays the role of a wing, and air is taken into the stirring shaft 24 with the rotation and the stirring shaft 24 is rotated.
As a result, the wafer buffer 28 is pushed out. The injection amount of the buffer buffer 28 can be adjusted by adjusting the inner diameter of the capillary tube and the viscosity of the buffer buffer.

FIG. 5 is a block diagram of the present residual chlorine meter, in which a detection electrode 9 exposed to a sample liquid and a comparison electrode 8 (dissolved gas state or ionized chlorine in the sample liquid passes through the microporous ceramic 17). The signal processing and control circuit 32 measures the effective chlorine concentration in the free residual chlorine based on the potential difference between the silver wire 15) exposed to the electrolyte 13 in the electrode tube 12 and the signal. Display unit 4
Sent to and displayed.

The free residual chlorine in the water (residual chlorine) is determined by using hypochlorous acid (HOCl) and hypochlorite ion (OCl-
). It is well known that the ratio of the two changes depending on the temperature and pH of the dissolved liquid. However, hypochlorous acid (HOC)
The sensitivity of the electrode for detecting 1) also changes depending on the temperature of the aqueous solution. This is because the sensing electrode uses a noble metal such as platinum, so that the sensing ability changes depending on the temperature.

As a method for preventing this, a temperature sensor 20 is arranged in the detection electrode 9, a constant for amplifying a signal obtained from the detection electrode 9 using a signal of the temperature sensor 20 is determined, and It is conceivable to correct measurement errors due to temperature. To perform this correction, a first-stage amplification temperature correction circuit unit 33 is provided.

[0028]

As described above, the present invention has a compact structure, is portable, does not require visual or other operations requiring skill, and is easy to handle. Further, the amount of residual chlorine in the sample solution is automatically determined. Can be measured with high accuracy,
There is an effect that inspection of tap water, pool water, industrial water and the like can be performed sufficiently and efficiently.

Also, unlike a general exposure type electrode, the reference electrode is immersed in the electrolytic solution, so that it is not only possible to save time and effort for polishing, but also because the diaphragm of the detection unit electrode is not used, a troublesome diaphragm is required. There is an effect that the replacement of the electrolyte is not required. Since the test solution collection cup attached to the main body is closed after the sample solution is collected, the residual chlorine does not scatter during the measurement, and the measurement error can be minimized.

Further, since the comparative electrode employs an electrolytic solution method, it is possible to measure a sample liquid such as seawater, color water, turbid water, etc. The electrolytic solution used for the comparative electrode is a gel type. In addition, since the electrode serves to protect the electrode from contamination of the sample solution, it is only necessary to wash it with water and wipe off moisture after the measurement, and there is an effect that handling and operation are very easy. In addition, since the comparative electrode is of a cassette type, replacement is easy.

[Brief description of the drawings]

FIG. 1 is a perspective view of one embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of an electrode portion of a sample collection cup in the embodiment shown in FIG.

FIG. 3 is a longitudinal sectional view of a stirring assembly part of a test solution collection cup in the embodiment shown in FIG. 1;

FIG. 4 is a cross-sectional view of a stirring shaft according to the present invention.

FIG. 5 is a block diagram of an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Instrument main body 2 Detection part 4 Display part 6 Sample collection cup 7 Electrode support cap 8 Reference electrode 9 Detection electrode 10 Electrode support plug 12 Electrode tube 13 Electrolyte 14 Film 15 Silver wire 17 Microporous ceramic 23 Stirring assembly

Claims (6)

[Claims] 1. An instrument main body having a signal processing and control circuit section, a power supply circuit section, and a display section, and a detecting section connected to the instrument main body via a connection cable, wherein the detecting section is a test solution. It is composed of a collection cup and an electrode support cap that is removably fitted to the collection cup, wherein the electrode support cap includes a comparison electrode and a detection electrode that are immersed in a sample solution in the test solution collection cup, and the comparison electrode is A portable residual chlorine meter characterized in that a metal wire having a metal coating applied only to a portion in contact with the electrolytic solution is hung in an electrode tube filled with the electrolytic solution. 2. The portable residual chlorine meter according to claim 1, wherein the metal film of the comparative electrode is silver-silver chloride, and the metal wire is a silver wire. 3. The portable residual chlorine meter according to claim 1, wherein a microporous ceramic is loaded at the bottom of the electrode tube of the comparative electrode. 4. The portable residual chlorine meter according to claim 1, wherein a gel electrolyte is used as the electrolyte in the electrode tube. 5. The portable residual chlorine meter according to claim 1, wherein the electrode support cap further includes a stirring assembly that is immersed in the sample solution in the test solution collection cup. 6. The portable residual chlorine meter according to claim 1, wherein said stirring assembly includes means for supplying a small amount of a buffer solution into a sample solution.