JPS6049250B2 - Standard solution for calibration check of residual chlorine meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a standard solution for checking the calibration of a residual chlorine meter.

In various water treatment systems, including water supply systems, we kill microorganisms, fungi, algae, shellfish, etc. that live in the water supply, making the water completely usable, and preventing material corrosion in the water supply system caused by these organisms. Chlorination is becoming popular for this purpose.

The injected chlorine reacts with ammonia nitrogen in the water,
It exists in the form of bound residual chlorine, which has inferior sterilizing power, and unbound residual chlorine, which has superior sterilizing power.

A residual chlorine meter is used to measure the effectiveness of this chlorination treatment. Methods for measuring residual chlorine include a colorimetric method, an iodine titration method, and a polarographic method.

In particular, the polarographic method is becoming popular because it allows continuous measurement of residual chlorine. One example is a method using a rotating platinum electrode. To measure free residual chlorine using this method, there is a method in which the detection liquid is made acidic and free chlorine is electrolytically reduced using a rotating platinum electrode. In other words, the equilibrium of the following reaction is shifted to the right side by the added reagent, and the generated Cl
. is reduced using a rotating platinum electrode. H++C1O→HCI
O(1) HC1O+H++Cl-→Cl2+ H2O(2)
C12+2-→2Cl- (3) In order to obtain reliable measured values in measurement methods using such equipment, it is necessary to check its calibration. A calibration check is also performed.

There are two ways to check the calibration of a residual chlorine meter: one is based on standard analysis, and the other is based on a standard solution with a known concentration. The former method involves, for example, analyzing sample water for free residual chlorine using a manual analysis method such as current adjustment specified in the Clean Water Testing Method, and then adjusting the scale of the meter to this analytical value. However, this method requires the preparation and management of analytical equipment and analytical reagents, and has the disadvantage that it requires additional skill and effort for analysis. On the other hand, in the latter method, a reference solution with a known concentration is introduced into the residual chlorine meter instead of the sample water, and the reading on the meter is adjusted to the concentration value. Conventionally, a sodium hypochlorite solution has been used as this type of standard solution. This solution exhibits similar behavior to hypochlorous acid, which is produced when chlorine gas is dissolved in water, and is therefore suitable as a standard solution for residual chlorine meters; however, it is unstable in concentration. Therefore, its concentration must be determined immediately before use. Moreover, since the reagent (sodium thiosulfate) required for this standardization is not sufficiently stable, its concentration must be standardized before use. In this way, the method using sodium hypochlorite solution requires analysis equipment, reagents,
Furthermore, there are drawbacks that require special skills and effort. If a technique to store sodium hypochlorite solution stably for a long period of time is established, this solution will have the following properties and will become a good standard solution for checking the calibration of residual chlorine meters.
(1) Provide a component that is representative of the measurement item and is the same as the measurement component or is compatible with the measurement principle.

(2) Does not adversely affect detection skills during calibration checks and thereafter. (3) When used as a standard solution, it is close to the properties of the test water actually measured.

Sodium hypochlorite (NaCIO) solution can be used directly. However, as mentioned above, it is unstable and cannot be stored for a long time.
According to various experiments conducted by the present inventors, sodium hypochlorite was used to reduce the concentration of about 10 Cfi, which is the concentration actually used.
．． It will last for up to 3 months if kept at an alkaline level of 1N or higher and stored in a UV-protected storage container. - It was found that the product could be stored without any change in concentration over the entire range.

In addition, to adjust the concentration of the standard solution that is actually used, it is recommended to dilute the above-mentioned high-concentration standard solution (high-concentration standard solution) to about 1 to 100%, especially about 10%. It was also found that the sodium hydroxide was sufficiently diluted and had no effect on the measurements. Next, the experimental results are shown.

I Air Blowing Test In order to confirm the degree of chlorine content scattered into the air from the standard stock solution, an accelerated test was conducted using the configuration shown in Figure 1.

In FIG. 1, 1 is a filter, 2 is a gas suction pump, 3 and 4 are gas flow meters, 5 and 6 are humidity control tanks, and 7 and 8 are air blowing tanks. Humidity control tanks 5 and 6 each contain pure water, and air blowing tanks 7 and 8 contain a test liquid, respectively. Furthermore, reference numerals 12 and 14 are relatively containers, and test liquids are placed in the containers 12 and 14, respectively. Table 1 shows the results of the tests conducted using FIG.

Note that the initial NaClO concentration of the test solution is expressed as a Cl2 equivalent value.

Moreover, the NaOH concentration indicates the concentration of added NaOH. As is clear from Table 1, it was found that the amount of scattering was significantly reduced by NaOH alkalinity of 0.1N or more.

■ Ultraviolet irradiation test As shown in Figure 2, the standard stock solution was placed in a storage solution 15 such as a white transparent glass pin, brown polyethylene pin, brown transparent glass pin, white glass pin, brown transparent glass pin, etc., and irradiated with ultraviolet rays. UV irradiation is performed using the lamp 20,
The degree of decomposition of chlorine content was confirmed.

In addition, in FIG. 2, 21 is a power source for the lamp 20, and 22 is a light shielding plate. The test results shown in FIG. 2 are shown in Table 2. The initial NaClO concentration of the test solution is expressed as a Cl2 equivalent value, and the test solution volume is 400 rT1.
It is 1.

Regarding the storage container types, A represents a white transparent glass pin, B represents a brown transparent glass pin, and C represents a brown transparent polyethylene pin. As is clear from Table 2, it was found that when brown polyethylene pins were used as the storage container, the rate of decrease in concentration was extremely small.

■Long-term storage test Figure 3 shows the results of a test on the reduction in chlorine content during long-term storage with different concentrations of NaOH and types of storage containers.

In this Figure 3, the chlorine reduction rate is initial concentration It is expressed as.

The characteristic line A is Cl.

2l6PPM equivalent NaClOaq (1N NaOH)
Characteristic line when stored in a brown polyethylene pin, the opening is NaClOaq (0.1N●N
Characteristic line when aOH property) is stored in a brown polyethylene pin, C is Cl.

This is a characteristic line when NaClOaq equivalent to 175 PPM (diluted with pure water) is stored in a brown glass pin. From FIG. 3, it was found that there was no significant difference in NaOH concentration between 0.1N and 1N. As explained above, 200P in terms of chlorine
A NaClO solution of PM level is converted into NaOHO. If it is made into an alkaline NaOH solution of about 1 to 1N and stored in a brown polyethylene pin, it can be stored with a concentration stability of about 0.5 to 1%/3 months, and when used, it will be 1 to 1000 times more concentrated, especially 1.
Dilute to approximately 0.00 times and use as a standard solution for residual chlorine meter.

[Brief explanation of the drawings] Figure 1 is a configuration diagram of the test equipment used to conduct air blowing tests on standard stock solutions. Figure 2 is a diagram showing the configuration of the test equipment used to test the stability of standard stock solutions. Figure 3 is a characteristic diagram of the chlorine content reduction rate versus test period. 15...Storage container.

Claims (1)

[Claims] 1. 1 to 1000 of the concentration of the standard solution introduced into the residual chlorine meter
Strong alkali was added to a hypochlorous acid solution containing double the chlorine content to a concentration of 0.1 to 1N, and the resulting solution was stored in an ultraviolet light-shielding storage container. A standard solution for checking the calibration of residual chlorine meters. 2. A standard solution for checking the calibration of a residual chlorine meter, characterized in that the strong alkali in the standard solution according to claim 1 is NaOH or KOH. 3. A standard solution for checking the calibration of a residual chlorine analyzer according to claim 1 or 2, wherein the storage container is a brown polyethylene bottle.