JPS5834353A - Oxygen meter - Google Patents

Abstract

PURPOSE:To measure the concentration of O2 and H2O2 dissolved in a liquid at the same time, by providing each pair of anodes and cathodes in a diaphragm type oxygen electrode and applying different applying voltage between each electrode. CONSTITUTION:O2 and H2O in a sample water enter into an electrolytic solution 13 passing through a diffusion film 2 provided on a sensor main body 1 which constitutes an oxygen meter. Cathodes 3, 4 and anodes 5, 6 are provided in the electrolytic solution 13. A battery 9 and an ammeter 18 are connected between the anode 5 and the cathode 3 and electric potential for reducing only H2O2 in the sample water is applied and then, an electric current A1 at this time is measured. Further, a battery 12 and an ammeter 11 are connected between the anode 6 and the cathode 4 and the electric potential for reducing O2 and H2O2 is applied and then, an electric current A2 at this time is measured. O2 is measured separately from H2O2 in a short time because the concentration of H2O2 in the sample water corresponds to the current A1 and that of O2 corresponds to the current A2-A1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oxygen meter, particularly an oxygen meter that simultaneously measures the concentration of 02 and H2O2 in an aqueous solution in which oxygen (0□) and hydrogen peroxide (H2O2) coexist and are dissolved. Regarding the meter.

Conventionally, a diaphragm-type oxygen electrode has been known as an underwater dissolved oxygen meter at room temperature and pressure. In addition, a pressure-coupling lance-type dissolved oxygen meter that can measure this even under high temperature and high pressure conditions is being considered. These methods have the disadvantage that if H2O2, which causes an electrode reaction similar to that of 0□, is present in the target solution, it is impossible to distinguish between the two, and it is measured as dissolved 02.

The object of the present invention is to solve the problem of 02 and H2 dissolved in a liquid.
An object of the present invention is to provide an oxygen meter capable of simultaneously measuring 0□ concentration.

The present invention provides a diaphragm type oxygen electrode with 02, H2O
This method was developed based on the fact that there is a difference in the applied voltage that gives the limiting current due to 0□ and H2O2, and is characterized by applying separate applied voltages to each of 0□ and H2O2.

An oxygen meter which is a preferred embodiment of the present invention will be described below with reference to FIG. O2 and H2O2 in the primary cooling water sampled from the boiling water reactor, that is, in the sample water, passes through the sensor body (3) that constitutes the oxygen meter. 13
cathodes 3 and 4 provided in the sensor body 1 filled with
reach. Here 0□ and H2O2 are reduced,
It becomes OH- ion according to the following reaction.

02+2H20+4e-→40H-・=-・=fllH
202+2e'''→20H''' ・------
・-(2+For reactions in equations (1) and (2), if the absolute value of the applied voltage between the anode and cathode provided in the sensor body is small, the reaction at the cathode becomes rate-determining.The absolute value of the applied voltage As you increase the value, it becomes 0□ or H20□
The diffusion rate in the diffusion film 2 becomes rate-determining, and saturation occurs in the output current. If the applied voltage is fixed at a point where the output current is saturated, the output current will be proportional to the O3 or H2O2 concentration in the sample water. Figure 2 shows temperature 2.
The relationship between the applied voltage and output current at 00t11' is 0□
The results of an investigation on and H2O2 are shown. H2O2 is 02
Saturation can be seen in the output current when the absolute value of the applied voltage is low compared to . Therefore, if an applied voltage V is selected such that (4) saturation is observed in the output current for H2O2 and no reduction reaction occurs at the cathode for 0□, the output current It can be considered that 0 again
If an applied voltage of 2 is chosen, where saturation is seen in the output current compared to 2, then reduction currents due to H202 and 02 will be obtained. In FIG. 1, the cathode is divided into two parts, a cathode 3 and a cathode 4. By the electric wire 7, the cathode 3. Ammeter 8
．． Connect battery 9 and anode 5. A potential vl is applied between the anode 5 and the cathode 3. At the cathode 3, only H20□ is reduced according to equation (2), and a current A flows between it and the anode 5. This current is measured with an ammeter 8.

An electric wire 10 connects the cathode 4. Ammeter 11. Connect battery 12 and anode 6. A potential v2 is applied between the cathode 4 and the anode 6. At the cathode 4, both 02 and H2O2 are reduced according to equations (1) and (2), and a current A2 flows between the cathode 4 and the anode 6. This current is measured with an ammeter 10. Therefore, for H2O2, the current value A is 0
．． The current value (A, -A,) corresponds to the current value (A, -A,). Input the measured values of ammeters 8 and 11 into the calculator (
A2-AI) may also be calculated.

The applied potentials v1 and v2 can be adjusted to predetermined values by selecting batteries with different electromotive forces, by changing the number of batteries, or by providing a variable resistor when using batteries with the same electromotive force. Can be adjusted.

The cathode 3 is a cathode for reducing H2O2, and the cathode 4 is a cathode for reducing H2O2. Note that in the anode 5 and the anode 6, the electrolyte 1
Although it depends on the combination of 3 and the electrode, the reaction shown in equation (3) proceeds.

Ag+CL−-, kgCL+e−−・−−−−−−(
3) The sensor body 1 and the diffusion membrane 2 in this embodiment are preferably made of heat-resistant and electrolyte-resistant materials such as tetrafluoroethylene resin. In particular, the diffusion film 2 is 0
It is necessary to allow □ and H2O2 to permeate easily, and to prevent the permeation of + and Ct'' in the electrolytic solution, or impurity ions such as Cog + and Cu2+ in the aqueous solution. and 6 is Ag/
Since AgCt/Ct'' is used, KCL is used as the electrolyte.
Use a basic aqueous solution of

In addition, as the anodes 5 and 6, A, g/A, gBr/
'Br'''Although it is still possible to use electrodes such as Ag/AgI/I-, the cathodes 3 and 4 may be made of materials that have a slight ionization tendency compared to Ag, and that are not easily corroded by oxygen. A11.pt etc. are mentioned.

Another embodiment of the present invention will be described below with reference to FIG.

FIG. 3 schematically shows an oxygen meter in which cathodes 14 and 15 are arranged in series. The cathode 15 is installed close to the diffusion membrane 2, and the cathode 15 is provided with many small through holes 16. A voltage V of 0□ is applied to the cathode 15, which has a potential sufficient to reduce H2O2, but does not cause reduction.

The cathode 14 is installed behind the cathode 15 (on the side farther from the diffusion membrane 2). A potential v2 sufficient to reduce 02 is applied to this cathode 14. Further, in order to bring the electrolytic solution 13 into contact with the cathodes 15 and 14, one or more through holes are provided in the cathode 14. I20□ in the sample water first passes through the diffusion membrane 2 and then reaches the cathode 15. Here H2
Only 0□ is reduced, and 0□ passes through the through hole 16 of the cathode 15. At this time, some H2O2 also diffuses through the through hole 16, but if the thickness of the cathode 15 is made sufficiently large relative to the diameter of the through hole 16, almost all of the H2O2 is reduced while passing through the through hole 16. Ru. Figure 4 shows H2 as a function of the through hole and thickness ratio.
The reduction rate of O2 is shown. The 02 that has passed through the through hole 16 reaches the cathode 14 and is reduced there. The current A between the cathode 15 and the anode 5 is proportional to the H2O2 concentration, and the current A2 between the cathode 14 and the anode 6 is proportional to the 02 concentration. H2O2 and 02 concentrations can be measured separately as in the previous example.

As described above, according to this embodiment, 02.0% in aqueous solution. The concentration of H2O2 can be measured simultaneously.

According to the present invention, since the sampling liquid is brought into direct contact with the diffusion membrane and the electrode reaction is utilized, the 02. H2O2 concentration can be measured separately in a short time. (2) Since 202 has a relatively short lifespan (on the order of minutes), it has become possible to measure components that could not be detected by conventional measurement methods, ie, methods such as chemical analysis of sampling liquid.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a preferred embodiment of the present invention, FIG. 2 is an explanatory diagram showing the relationship between potential and output current, which is the basis of the present invention, and FIG. FIG. 4, which is a vertical cross-sectional view when the cathodes are arranged in series, is an explanatory diagram showing the H2O2 yield with respect to the ratio of the thickness of the cathode and the radius of the through hole. 1... Sensor main body, 2... Diffusion film, 3, 4. t4゜15...Cathode, 6...Anode, 7.10...Electric wire,
8゜Figure 7〆p Force U oath and 4Σd and V no

Claims (1)

[Claims] 1. A container having an opening and filled with an electrolytic solution, a diaphragm attached to the container covering the opening, and a diaphragm that is in contact with the electrolytic solution and attached to the container. An oxygen meter comprising a pair of anodes and a cathode, each comprising a pair of anodes and a cathode, a first circuit connecting one of the anodes and a cathode, and a second circuit connecting the other anode and cathode. An oximeter, characterized in that a first power source and a first current detection means are provided in the first circuit, and a second power source and a second current detection means are provided in the second circuit. 2. Claim 1, wherein the potential applied between the anode and cathode connected to the first circuit is different from the potential applied between the anode and cathode connected to the second circuit. oxygen meter. 3. a container having an opening and filled with an electrolyte, and a diaphragm attached to the container so as to cover the opening;
In an oxygen meter comprising an anode and a cathode that are in contact with the electrolyte and are attached to the container, a cathode for H2O2 reduction having a plurality of through holes is attached to the container in contact with the electrolyte, An anode is attached to the container in contact with the electrolytic solution, and a cathode for 02 reduction is placed in contact with the electrolytic solution at a distance from the diaphragm that is greater than the distance between the diaphragm and the cathode for reducing H2O2. The H2
The 0□ reduction cathode and the H2O2 reduction anode are connected, and the 0□ reduction cathode and the 0□ reduction anode are connected by a second circuit having a second power source and a second current detection means. Oxygen meter.