JPH03273152A - Method for calibrating instrument for measuring oxdiative gas - Google Patents

Abstract

PURPOSE:To make exact calibration with simple operations in a short period of time by calibrating a measured value as the corresponding chlorine dioxide concn. or the concn. corresponding to the corresponding chlorine dioxide concn. of another oxidative gas. CONSTITUTION:An Aq. soln. of NaClO2 of, for example, 1.30X10<4>M concn. and a sulfuric acid soln. of 2.4 pH contg. KCl of 0.1M concn. are put into separate containers and are preserved for 100 days at ordinary temp. Then, 50ml aq. NaClO2 soln. and 50ml sulfuric acid soln. contg. 0.1M KCl are mixed in a hermetic container of 120ml capacity and the pH of the aq. soln. mixture is adjusted to 2.7. The aq. soln. mixture in which gaseous ClO2 is dissolved at 6.2mg/l is obtd. as a liquid phase under the above-mentioned conditions from the previously obtd. relation between ClO2<-> and ClO2. The instrument for measuring the gaseous ClO2 is then calibrated to 6.2mg/l with the aq. soln. mixture as a standard liquid. The plural solns. which are so adjusted as to have 11.4mg/l concn. of the dissolved gaseous ClO2 are continuously measured by the instrument for measuring the gaseous ClO2 after the calibration. The instrument for measuring the gas, such as chlorine dioxide, is easily and exactly calibrated in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for calibrating an apparatus for measuring oxidizing gases such as chlorine dioxide and ozone.

[Conventional technology]

Chlorine dioxide (atO> and ozone (0) have strong oxidizing power, so for example, chlorine dioxide is used to bleach textiles, etc., and recently, as a disinfectant instead of chlorine, it is used to sterilize tap water and pool water. It is used for deodorizing water, etc.

Concentrations of oxidizing gases such as chlorine dioxide, ozone, and Due to these drawbacks, recently a diaphragm-type polarographic electrode method using a diaphragm that selectively permeates chlorine dioxide, ozone, chlorine, etc. (Japanese Unexamined Patent Publication No. 125095/1982) has been developed.
An oxidizing gas measuring device is used. Furthermore, with a diaphragm electrode type oxidizing gas measuring device that measures the potential with a diaphragm electrode using a similar diaphragm, it is possible to measure both dissolved oxidizing gas solutions and gaseous oxidizing gases.

The above-mentioned oxidizing gas measuring devices can obtain the oxidizing gas concentration as an indicator simply by bringing an electrode equipped with a diaphragm into contact with a sample liquid or sample gas, so they are simple and suitable for continuous measurement, but they are As with any chemical measurement device, calibration is required.

Conventionally, oxidizing gas measuring devices have been calibrated using the oxidizing gas to be measured, but the oxidizing gas used for calibration naturally needs to be adjusted to a constant concentration. For example, to adjust a dissolved CtO gas aqueous solution with a certain concentration, cto
A method is used in which gas is generated, the CtO gas is collected in pure water, and its concentration is determined by iodometric titration, but this adjustment operation is troublesome.

Moreover, all oxidizing gases are unstable, and decomposition progresses during short-term storage in either the gas phase or the dissolved state, resulting in a decrease in titer or concentration. For example, chlorine dioxide (C
In the case of a dissolved OTO gas aqueous solution in which tO) gas is dissolved in pure water, as shown by the dotted line in Figure 4, a brown polypropylene bi-), a narrow-mouth brown glass pin (△), and a wide-mouth brown glass pin (b) are used. Even when stored, it decomposes in a very short period of time and the concentration of dissolved 010 gas decreases. The same situation applies to ozone gas, chlorine gas, and the like.

On the other hand, it is almost impossible to store the oxidizing gas to be measured or its dissolved aqueous solution at a constant concentration for a long period of time as a standard solution or rubbing solution for calibration. Although it is necessary to prepare it as a standard solution, it is extremely complicated as the troublesome preparation operation is repeated each time, and therefore, there is a drawback that calibration requires a long time.

[Problem to be solved by the invention]

SUMMARY OF THE INVENTION In view of the conventional circumstances, it is an object of the present invention to provide a method for calibrating an oxidizing gas measuring device that allows accurate calibration in a short time with simple operations.

[Means to solve the problem]

In order to achieve the above object, the method for calibrating the oxidizing gas measuring device of the present invention is to use a chlorite ion aqueous solution in which chlorite is dissolved and an acid in which chloride is dissolved, or the chlorite ion aqueous solution and an acid. and chloride or an aqueous solution containing chloride are stored in separate containers, and when calibrating the oxidizing gas measuring device, each liquid is mixed in a predetermined amount in a closed container to quantitatively measure chlorite ions. chlorine dioxide gas with a known concentration obtained in a sealed container or dissolved chlorine dioxide gas with a known concentration in a mixed aqueous solution with the measuring device, and the indicated value is used as the chlorine dioxide concentration. or calibrate the concentration of other oxidizing gas as corresponding to the chlorine dioxide concentration.

[Effect]

When the pH of the solution is lowered in the presence of chlorine ions (C1), chlorite ions (C10) quantitatively and rapidly change to chlorine dioxide (C!10) at a certain p l (. Therefore, the above If the operation is carried out quantitatively in a closed container,
Since the generated CtO gas is in an equilibrium state between the gas phase and the liquid phase, the gas phase in the sealed container contains a certain concentration of clo gas, and the generated CIO gas is collected and separately dissolved in pure water. Even if this is not done, a certain concentration of atO gas is dissolved in the liquid phase (mixed aqueous solution).

That is, as shown in FIG.
1) When sulfuric acid is added to NaC10 aqueous solutions with different concentrations of 101 M to lower the pH, the mixed aqueous solutions, which are the liquid phase in the sealed container, will each reach a predetermined concentration at a nearly constant pH value depending on the KOI 9 degrees. The result is an aqueous solution containing dissolved CtO gas. For example, when the KC1 concentration is 101M, from Figure 1, approximately pi ("In the book, C10- changes to CtO, and the mixed aqueous solution contains 4.2 m9/l of 010
Gas is dissolved.

Often, under a predetermined KOl concentration, C10- is ct
By determining the pH that changes to o and the quantitative relationship between cto- and C1O, under certain conditions, a known concentration of CtO
Since the gas and atO solution are obtained in a closed container, this can be used as is for calibration.

Note that the sealed container does not have to be a completely sealed state where no gas flows, but may be a container that is sealed to the extent that almost no gas escapes to the outside before the CtO gas reaches a gas-liquid equilibrium state. For example, a small hole such as a pinhole may be present.

Moreover, CtOJ used for producing CTO for standard solution or standard gas is extremely stable in the solution, as shown by the solid line in FIG. 4, and no change in concentration is observed even after long-term storage. Therefore, from a stored CtO solution with a known concentration, a CIO solution or CtO gas with a known concentration can be easily obtained whenever needed, and this can be used as a standard solution or standard gas to measure CtO gas in the dissolved or gas phase. It is possible to calibrate the device easily and accurately.

Also, for other oxidizing gas measuring devices such as 0 gas and chlorine gas, if the sensitivity relationship between the oxidizing gas and chlor gas is determined in advance, calibration can be performed using CtO and gas according to the above method. Is possible.

(Example) Example 1 A sulfuric acid solution (pH 2,4) containing a Na(310 aqueous solution with a concentration of 1.30×10-'M and KO/with a concentration of 0.1M) was placed in separate HfM and stored at room temperature for 100 days. .next,
In a closed container with a capacity of 120 liters, 50 liters of the above NaCl aqueous solution was added.
- and 0.1 MKC/containing sulfur, acid solution 5o-,
The pH of the mixed aqueous solution was set to 2.7. C10- determined in advance
From the relationship between
It was known that a mixed aqueous solution containing 6.2rn9/l of O gas dissolved therein could be obtained.

Using the mixed aqueous solution obtained in the above procedure as a standard solution, a C2O gas measuring device (CLO-20? manufactured by Toa Denpa Kogyo ■) using a diaphragm-type polarographic electrode was calibrated to 6.2 T/l. Next, the dissolved CIO gas concentration is determined to be 1) by the calibrated C1O gas measuring device. When a plurality of solutions adjusted to have C++s/l were continuously measured, the response curve shown in FIG. 2 was obtained, and it was found that good reproducibility and response were obtained.

Example 2 IJaCIO aqueous solution and K
Concentration 6 as a gas phase in a closed container containing a sulfuric acid solution containing Ct.
．． 2WQ/l of C10 gas was obtained. Regarding the prototype diaphragm electrical connection type 0 gas measuring device, the relationship between the sensitivity of CIO gas and O gas was determined in advance, and from this sensitivity relationship, the above 6.2yn
Using iy/l of CIO gas, the same O gas establishment device was installed at 15
．． It was calibrated to 51n9/l.

Next, using the above-mentioned 0 gas measuring device after calibration, and also using the diaphragm electrode type chlorine gas measuring device, by determining the relationship between cIO gas, Cl, and gas sensitivity in the same manner as in the case of 0 gas, Calibration can be performed using CjlO gas.

〔Effect of the invention〕

According to the present invention, chlorine dioxide of a known concentration in the gas phase or dissolved in the liquid phase can be obtained by a simple mixing operation of multiple liquids that can be stored for a long period of time, so that it can be used as it is as a standard gas or standard solution. , oxidizing gas measuring devices such as chlorine dioxide, ozone, and chlorine can be easily and accurately calibrated.

[Brief explanation of drawings]

Figure 1 shows constant concentrations of Nacl with different MCI concentrations. Figure 2 is a graph showing the relationship between pH and dissolved chlorine concentration when an aqueous solution is made acidic with sulfuric acid, and Figure 2 is a response curve of a diaphragm type polarographic N-pole type chlorine dioxide gas measuring device calibrated by the method of the present invention. , Fig. 3 is a response curve of the diaphragm electrode type ozone gas measuring device calibrated by the method of the present invention, and Fig. 4 is a graph showing the change in ei degree with the change in storage time of the dissolved ○lo2 aqueous solution and the dissolved CtOJ solution. It is.

Claims (1)

[Claims] (1) Storing an aqueous chlorite ion solution in which chlorite is dissolved and an acid in which a chloride is dissolved, or the aqueous chlorite ion solution and an acid and chloride, or an aqueous solution in which a chloride is dissolved, in separate containers, When calibrating the oxidizing gas measuring device, chlorite ions are quantitatively converted into chlorine dioxide gas by mixing predetermined amounts of each of the above liquids in a sealed container, and chlorine dioxide with a known concentration is obtained in the sealed container. Measure dissolved chlorine dioxide gas at a known concentration in the gas or mixed aqueous solution with the measuring device, and use the indicated value as the chlorine dioxide concentration, or calibrate it as a concentration corresponding to the chlorine dioxide concentration of another oxidizing gas. A method for calibrating an oxidizing gas measuring device, characterized in that: