Method for acquiring oxidation-reduction state of aqueous solution as hydrogen electrode potential, method for acquiring effective hydrogen gas partial pressure of aqueous solution, and device for acquiring oxidation-reduction state of aqueous solution as hydrogen electrode potential

Abstract

To provide a method and device for acquiring the oxidation-reduction state of an aqueous solution as a hydrogen electrode potential.SOLUTION: A hydrogen electrode potential of an aqueous solution is defined by the Nernst equation. A method includes: a step for measuring the hydrogen partial pressure in the gas phase that is in equilibrium with the aqueous solution, the temperature, and pH of the aqueous solution; and a step for analyzing the hydrogen electrode potential from the inverse logarithm pH2 of the measured hydrogen partial pressure, the temperature, and the pH. For example, at the room temperature of 25°C (T=298.15K) and pH=7.0, the hydrogen electrode potential can be obtained from the equation: Eh≒29.6×pH2-59.2×pH≒29.6×pH2-414.4 (mV) and the approximate equation. When the pH is constant, a change in the hydrogen electrode potential of the aqueous solution can be obtained from the equation: ΔEh≒29.6×ΔpH2 (mV) and the approximate equation.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for obtaining the oxidation-reduction state of an aqueous solution as a hydrogen electrode potential, a method for obtaining the effective hydrogen gas partial pressure of an aqueous solution, and an apparatus for obtaining the oxidation-reduction state of an aqueous solution as a hydrogen electrode potential.

Background Art

[0002] An aqueous solution has electrochemical properties and is measured as an electrode potential. The oxidation-reduction potential Oxidation Reduction Potential (ORP) is an index indicating the oxidizing and reducing properties of an aqueous solution, and is measured using a potentiometer main body, a noble metal electrode (platinum electrode or gold electrode), and a reference electrode. Since the potential is affected by temperature, it is necessary to measure at a constant temperature. Oxygen O 2 and hydrogen H 2 are generated by electrolysis, so the potential window is narrow (1.24V). Also, when hydrogen ions are included in the oxidation-reduction reaction, the equilibrium potential depends on the pH of the aqueous solution.

[0003] Generally, the oxidation-reduction potential ORP of an aqueous solution increases (oxidizes) due to oxygen O 2 and hydrogen ions H + and decreases (reduces) due to hydrogen H 2 . Since the gaseous oxygen and hydrogen act as ideal gases even in an aqueous solution, the partial pressure of the aqueous solution is equal to the partial pressure of the gas phase in the equilibrium state. The oxidation-reduction potential ORP changes in proportion to the partial pressures of oxygen and hydrogen according to the Nernst equation. A standard hydrogen electrode is used as a reference electrode, and the hydrogen partial pressure is defined as 1 atm. When used in an experiment, it is composed of inserting a platinum electrode into hydrochloric acid with an average activity of 1 saturated with bubbling of 1 atm of hydrogen gas, and is defined as zero (0) mV at 25°C.

[0004] Dissolved oxygen (DO) and pH (hydrogen ion activity) that affect the oxidation of an aqueous solution are measured using an electrode potential. For dissolved oxygen, a diaphragm with excellent oxygen permeability is used, and the permeated oxygen concentration is detected by an electrode. In pH measurement using a glass electrode, an electromotive force is generated in proportion to the difference in pH between the inside and outside of the glass thin film, so the pH is measured from the electromotive force between the reference electrode.

[0005] On the one hand, among the factors affecting the reduction of an aqueous solution, there is the relative hydrogen score (rH) proposed by Clark in 1923. rH is the logarithm of the reciprocal of the hydrogen partial pressure (-log[hydrogen partial pressure]), and the nominal range is from 0 to 42. In the 1950s, it was cited by deClerck as a measure for beer brewing. In the study of redox systems in aquariums and various seas and oceans, a mathematical relationship has been reported among the redox potential ORP, pH, and rH. For example, in 2008, Homes-Farley reported an empirical approximation formula using the redox potential ORP and pH of an aqueous solution: rH = ORP / 29 + 2×pH + 6.67. That is, by using rH calculated from the actually measured redox potential ORP and pH, an indicator of the redox state of the underwater environment has been established.

[0006] The half-reaction by hydrogen is between hydrogen ions H + in an aqueous solution and gaseous hydrogen gas H 2 and is

Number

[0007] and according to the Nernst equation, the electrode potential is proportional to the logarithm of [H + (aq)] / [ H 2 (g)]. [H + (aq)] is the hydrogen ion activity of the aqueous solution, and [ H 2 (g)] is the activity of the partial pressure of gaseous hydrogen gas. Hydrogen H 2 exists in trace amounts due to atmospheric, biological, geological, or artificial factors, but except for being used as a standard hydrogen electrode or a reversible hydrogen electrode, the measurement of the hydrogen electrode potential has not been carried out. The present invention relates to a method and an apparatus for measuring the hydrogen electrode potential by the effective hydrogen gas partial pressure.

[0008] In an aqueous solution, redox reactions occur through aerobic metabolism, anaerobic metabolism, and inorganic chemical reactions. Based on the Nernst equation, the standard redox potentials of various redox substances have been reported, and theoretically, the direction of each redox reaction can be predicted. However, the standard redox potential does not indicate at what rate the actual redox reaction occurs. On the other hand, in electrochemical reaction kinetics, it is assumed that both the cathodic reaction and the anodic reaction occur on the same electrode during the corrosion reaction of a metal, and the current flowing locally depends on the electrode potential, which is shown by the Butler-Volmer equation. The direction and rate of the reaction are defined by the electrode potential (natural potential) at which the total current of all the redox systems involved becomes zero. Therefore, for a redox reaction involving electron transfer, the reaction rate cannot be known without measuring the electrode potential.

[0009] Although dissolved oxygen does not directly react with water molecules, it changes the redox potential in the positive direction, i.e., towards nobility. In water quality tests, the dissolved oxygen concentration is measured, and it is known that when oxygen is present, the redox potential becomes +200 to +400 mV. For example, in the water quality management of boiler water treated with oxygen in a thermal power plant, with the detection of about 10 ppb of dissolved oxygen, the corrosion potential of the piping rapidly rises from about -400 mV to about 100 mV. When the electrode potential of the aqueous solution changes to the positive side due to an increase in dissolved oxygen or hydrogen ion concentration, according to the Butler-Volmer equation of electrochemical kinetics, the anodic (oxidation) reaction is accelerated and the cathodic (reduction) reaction rate decreases, indicating that the piping corrodes. The measurement of the corrosion potential of the piping is used as a water quality measurement method.

[0010] On the one hand, in the cooling system of a nuclear power plant, water molecules are decomposed by radiation, generating chemical species such as oxygen. Therefore, in the water quality management of nuclear power plants, the hydrogen injection method is used to prevent the oxidation-reduction potential from becoming noble due to dissolved oxygen. In 1987, guidelines for the hydrogen injection method for the recirculation system were published. By injecting 1 ppm of hydrogen, the dissolved oxygen concentration in the recirculation system decreases to 2 ppm, but the corrosion potential of steel is 0 mV or higher. Even at the same dissolved oxygen concentration, by injecting 1.3 ppm of hydrogen, the corrosion potential of steel is suppressed to -230 mV or lower, protecting the recirculation system piping. When the hydrogen gas partial pressure increases, the electrode potential of the aqueous solution changes to the negative side and becomes noble. The cathode (reduction) reaction is accelerated, and the anode (oxidation) reaction decreases, so the piping does not corrode. That is, when the dissolved oxygen in the aqueous solution is low, the oxidation-reduction state can be evaluated using the hydrogen electrode potential of the aqueous solution measured by the hydrogen partial pressure.

[0011] Under conditions of low oxygen, anaerobic respiration and fermentation occur. Decompose organic matter and reduce NAD + to NADH in the cathode (reduction) reaction and oxidize NADH to NAD in the electron transport system + The anode (oxidation) reaction is carried out in parallel. Therefore, since the oxidation-reduction potential of an aqueous solution with low dissolved oxygen depends on the hydrogen electrode potential, fluctuations in the hydrogen partial pressure directly affect the cathode and anode reaction rates. In fermentation such as anaerobic bacteria culture and brewing, the oxidation-reduction state is evaluated using the relative hydrogen score rH.

[0012] Under aerobic conditions with sufficient oxygen, the dissolved oxygen concentration is an important factor in the reaction rate. In aerobic respiration, oxygen is the final electron acceptor, and the oxygen partial pressure in the tissue depends on the diffusion rate. However, since the oxygen diffusion rate becomes the rate-determining step, the oxygen partial pressure in the aqueous solution remains constant even in the aerobic state. Even in aerobic respiration, decompose organic matter and reduce NAD + to NADH in the cathode (reduction) reaction and oxidize NADH to NAD in the electron transport system +The anodic (oxidation) reaction that oxidizes occurs in parallel. The decomposition reaction of organic substances depends on the oxidation-reduction potential of the aqueous solution, similar to anaerobic respiration. Therefore, the relative hydrogen score rH has been used for water quality management in aquariums and the evaluation of the oxidation-reduction state of seawater and the ocean. There are also reports that the oxidation-reduction potential ORP should not be used for hydrogen measurement.

[0013] Patent Document 1 below discloses a method and apparatus for measuring dissolved oxygen in a liquid using spectral information of light.

Prior Art Documents

Patent Documents

[0014]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0015] An aqueous solution is a substance in which solids, liquids, and gases are dissolved in water. The oxidation-reduction potential of an aqueous solution is affected by the concentration and ratio of dissolved oxidation-reduction substances, dissolved oxygen, and pH. With the measurement method and apparatus described in Patent Document 1, dissolved oxygen in an aqueous solution can be measured. In the present invention, not only the above-mentioned narrow sense of aqueous solution but also all water areas in nature, such as the ocean, lakes, and rivers, are included in the concept of aqueous solution. Dissolved oxygen and pH, which are oxidation factors of an aqueous solution, can be directly measured. However, dissolved hydrogen, which is a reduction factor of an aqueous solution, is approximated by the oxidation-reduction potential and pH as a relative hydrogen score. Therefore, it is required to measure the effective hydrogen gas partial pressure of an aqueous solution and directly calculate the hydrogen electrode potential of the aqueous solution.

Means for Solving the Problems

[0016] In the standard hydrogen electrode, the hydrogen ion activity is 1, which is the potential of a platinum electrode in equilibrium with hydrogen gas at 1 atm, and is used as the reference (0 V) for the redox potential. Hydrogen gas bubbles are generated so that the hydrogen gas partial pressure in the aqueous solution becomes 1 atm. The hydrogen electrode potential can be obtained from the Nernst equation based on the half-reaction of hydrogen:

Number

[0017] When measuring the hydrogen electrode potential of an aqueous solution, for example, in an aqueous solution used in a chemical reaction, a culture solution used for organisms, river water or seawater in nature, it is difficult to directly measure the hydrogen gas partial pressure due to solubility relationships. Therefore, in the present invention, the hydrogen partial pressure in the gas phase in equilibrium with the aqueous solution is used.

[0018] That is, according to the present invention, a step of obtaining the effective hydrogen gas partial pressure in the gas phase in equilibrium with the aqueous solution, a step of obtaining the temperature of the gas phase, a step of obtaining the hydrogen ion activity (pH) of the aqueous solution, a step of calculating the inverse logarithm (pH 2 ) of the partial pressure, a step of analyzing the hydrogen electrode potential of the aqueous solution using the temperature, the hydrogen ion activity (pH), and the inverse logarithm (pH 2 ) are provided, and a method for obtaining the redox state of an aqueous solution as the hydrogen electrode potential is provided. A method for obtaining the redox state of an aqueous solution as the hydrogen electrode potential is provided, which includes:

[0019] Also, according to the present invention, a step of mixing a part of the aqueous solution with a gas having a known hydrogen gas partial pressure in a sealed container and measuring the effective hydrogen gas partial pressure of the gas in the equilibrium state, a step of calculating the effective hydrogen partial pressure of the aqueous solution from the hydrogen partial pressure of the gas in the sealed container, A method for obtaining the effective hydrogen gas partial pressure of an aqueous solution is provided.

[0020] Furthermore, according to the present invention, a step of measuring the concentration of dissolved hydrogen gas in an aqueous solution, A step of calculating the effective hydrogen gas partial pressure of the gas phase in equilibrium with the aqueous solution using the concentration of the dissolved hydrogen gas and the solubility of the dissolved hydrogen gas; A method for obtaining the effective hydrogen gas partial pressure of an aqueous solution having the same is provided.

[0021] Furthermore, according to the present invention, a hydrogen gas partial pressure acquisition unit that acquires the hydrogen gas partial pressure of the gas phase in equilibrium with the aqueous solution, a temperature acquisition unit that acquires the temperature of the gas phase, a hydrogen ion activity (pH) acquisition unit that acquires the hydrogen ion activity (pH) of the aqueous solution, calculating the negative logarithm (pH 2 ) of the hydrogen gas partial pressure, and the negative logarithm (pH 2 ) is defined as the hydrogen gas index pH 2 and an arithmetic unit that analyzes the hydrogen electrode potential of the aqueous solution from the temperature and the hydrogen ion activity (pH); An apparatus for obtaining the oxidation-reduction state of an aqueous solution having the same as the hydrogen electrode potential is provided.

[0022] Note that when the hydrogen gas index pH 2 is defined as the negative logarithm (pH 2 =-log[hydrogen gas partial pressure (Pa) / 100 kPa]), performing the calculation of the hydrogen gas index pH 2 and reading out a predetermined arithmetic formula stored in the storage means:

Equation

[0023] calculating the hydrogen electrode potential according to the predetermined arithmetic formula, and displaying the obtained hydrogen electrode potential and pH 2 is a preferred embodiment of the method for obtaining the oxidation-reduction state of the aqueous solution of the present invention as the hydrogen electrode potential.

[0024] Also, the change in the hydrogen electrode potential is the hydrogen gas index pH 2Having a step of displaying as a variation thereof is a preferred embodiment of the method for obtaining the redox state of an aqueous solution of the present invention as a hydrogen electrode potential.

[0025] Further, having a housing to which the hydrogen gas partial pressure acquisition unit, the temperature acquisition unit, and the hydrogen ion activity (pH) acquisition unit are attached, forming a non-flow region where the flow of liquid and gas is disabled, and having a flow region or a membrane that allows at least the flow of hydrogen gas is a preferred embodiment of the apparatus for obtaining the redox state of an aqueous solution of the present invention as a hydrogen electrode potential.

[0026] Also, the hydrogen gas index pH 2 is defined as the negative logarithm (pH 2 = -log[hydrogen gas partial pressure (Pa) / 100 kPa]) of the effective hydrogen gas partial pressure, and performing the calculation of the hydrogen gas index pH 2 , reading out a predetermined arithmetic expression stored in the storage means:

Equation

[0027] and means for calculating the hydrogen electrode potential according to the predetermined arithmetic expression, means for displaying the obtained hydrogen electrode potential and pH 2 is a preferred embodiment of the apparatus for obtaining the redox state of an aqueous solution of the present invention as a hydrogen electrode potential. Having

[0028] In the method and apparatus for obtaining the redox state of an aqueous solution of the present invention as a hydrogen electrode potential, the effective hydrogen gas partial pressure, temperature, and hydrogen ion activity (pH) of the gas phase in equilibrium with the aqueous solution are respectively obtained. The effective partial pressure fugacity [H 2 of hydrogen gas is expressed as a ratio to the reference pressure P 0 . Using the reference pressure P 0 and the hydrogen gas partial pressure PH 2 ,

Equation

[0029] Then, the hydrogen electrode potential is obtained by the following equation including the gas constant R (8.31 J / K / ml), the absolute temperature K (K), and the Faraday constant F (96485 C / mol).

Number

[0030] Next, the hydrogen electrode potential is analyzed using the measured temperature, pH, and the inverse logarithm of the effective hydrogen gas partial pressure (pH 2 ). For example, when the temperature T is 25 °C (298.15 K), the hydrogen electrode potential is Eh = 0.0296 × pH 2 - 0.0592 × pH (V). When pH = 7.0, Eh = 29.6 × pH 2 - 414.4 (mV). That is, the hydrogen gas partial pressure, temperature, and pH of the aqueous solution in equilibrium with the gas phase can be measured to obtain the hydrogen electrode potential.

[0031] The change ΔEh in the hydrogen electrode potential of the aqueous solution is obtained from the change ΔpH 2 in pH when pH is constant 2 .

Number

[0032] Next, if necessary, the redox state is represented by the hydrogen electrode potential and the inverse logarithm of the hydrogen gas partial pressure (pH 2 ). For example, when the temperature is 25 °C (298 K),

Number

[0033] It can be approximated. Note that the display of the hydrogen electrode potential and the inverse logarithm of the hydrogen gas partial pressure (pH 2 ) is not essential at this stage, and electrical signals or the like indicating these may be output. That is, the hydrogen electrode potential and the inverse logarithm of the hydrogen gas partial pressure (pH 2 ) are notified to the measurer by voice using such electrical signals or the like, or such electrical signals or the like are transmitted to a remote location and displayed, printed, or various operations are performed using such electrical signals or the like.

[0034] Hydrogen gas is stable at normal temperature and pressure and does not undergo a chemical reaction with anything other than fluorine. The enzyme that catalyzes the reversible redox reaction of molecular hydrogen H 2 is hydrogenase, and this enzyme is important in anaerobic metabolism. Until now, the dissolved hydrogen concentration has been measured as an index of contamination in an aqueous solution under anaerobic conditions. On the other hand, hydrogen gas is present in trace amounts in the environment from atmospheric, microbial, geochemical, and artificial sources. Hydrogen gas is a powerful reducing agent, and even in trace amounts, it affects the electrode potential of an aqueous solution. Therefore, hydrogen gas is one of the factors that define the electrode potential of an aqueous solution.

[0035] In the present invention, the effective hydrogen partial pressure of the gas phase in equilibrium with the aqueous solution is measured by a housing formed from a non-flow region that prevents the flow of liquids and gases and a housing having a flow region or a membrane that allows at least the flow of hydrogen gas. The hydrogen partial pressure of the gas phase in equilibrium with the liquid in the closed space is measured. For an aqueous solution in an open space, a closed space in equilibrium with the aqueous solution is formed by a measuring device, and the hydrogen partial pressure of the gas phase in equilibrium is measured. Alternatively, a closed space in equilibrium with the aqueous solution to be measured is formed by a measuring device using a semipermeable membrane through which hydrogen gas passes, and the hydrogen partial pressure of the gas phase in the equilibrium state is measured.

[0036] As another method, a part of the aqueous solution is mixed with a gas having a known hydrogen gas partial pressure in a sealed container, and the effective hydrogen gas partial pressure of the gas in the equilibrium state is measured. The measurement can be carried out by inserting a measuring device housing into the sealed container, or by injecting the gas in the equilibrium state into, for example, a high-sensitivity sensor gas chromatography (SGHA-P3-A, Nissha EFIS Co., Ltd.) measuring device to measure the hydrogen concentration of 10 to 10,000 ppb (parts per billion) and obtain the hydrogen partial pressure. Next, the effective hydrogen partial pressure of the aqueous solution is calculated from the hydrogen partial pressure of the gas in the sealed container. As for the method of measuring the hydrogen gas partial pressure, if it is a potential detection type gas sensor, for example, the hydrogen gas partial pressure at a concentration of 0.1 ppm to 2% can be measured. Since the atmospheric pressure is 1 atm, the hydrogen gas partial pressure = 1 atm × hydrogen gas concentration. Also, the temperature of the gas phase and the pH of the aqueous solution are measured.

[0037] When directly measuring the dissolved hydrogen concentration, the hydrogen gas partial pressure is obtained from the dissolved hydrogen concentration according to Henry's law.

Number

[0038] Here, k H is the Henry's constant, C aq is the molar concentration of dissolved hydrogen, and P is the hydrogen gas partial pressure in contact with the liquid. Using the molecular weight of hydrogen 2.0, the hydrogen gas partial pressure = dissolved hydrogen gas concentration ÷ (Henry's constant × 2.0). As a method for solving the problem, the dissolved hydrogen gas concentration of the aqueous solution is measured, and the effective hydrogen gas partial pressure of the gas phase in equilibrium with the aqueous solution is calculated using the aforementioned hydrogen gas concentration and the solubility of hydrogen gas. For example, at 25 °C,

Number

[0039] and when the atmospheric pressure is 1 bar (atm), the hydrogen concentration is

Number

[0040] Therefore, the hydrogen gas partial pressure

Number

[0041] is obtained. The effective partial pressure of hydrogen [H 2 is represented by the ratio of the standard atmospheric pressure P 0 = 1 bar = 1×10 5 Pa and PH 2 . That is,

Number

[0042] When measuring the hydrogen partial pressure P X in the sealed container from the hydrogen gas partial pressure P H2 in the aqueous solution, when the temperature T (K) of the sealed container and the aqueous solution is set, the hydrogen gas partial pressure P A in the container before adding the aqueous solution is used, the volume of the gas phase in the sealed container is V A and the volume of the liquid phase is V S . Since the number of moles of gas before and after the equilibrium state is equal, using the gas constant

Number

Number

[0043] becomes. For example, at a temperature of 25°C (298.15 K),

Number

Number

[0044] It is required. The solubility of the gas is based on Compilation of Henry’s Law Constants for Inorganic and Organic Species of Potential Importance in Environmental Chemistry by Sander R.

Advantages of the Invention

[0045] According to the present invention, under the conditions where the dissolved oxygen can be regarded as constant, the oxidation-reduction potential of the aqueous solution is measured as the hydrogen electrode potential, and the change in the oxidation-reduction potential of the aqueous solution is pH 2 can be used for evaluation and the redox state can be controlled.

Brief Description of the Drawings

[0046]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0047] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a preferred embodiment of a temperature, hydrogen gas partial pressure, pH measurement unit 20A that constitutes a part of an apparatus for obtaining the redox state of an aqueous solution of the present invention by executing a method for obtaining the redox state of the aqueous solution of the present invention as a hydrogen electrode potential. The diagram shows a case where the gas in contact with the aqueous solution 9 to be measured in a closed space is in an equilibrium state. The apparatus shown in FIG. 1 has a housing 1 that is arranged in proximity to and in non-contact with the water surface 8A of the aqueous solution 9 to be measured. In a laboratory, the aqueous solution 9 is contained in an appropriate container (not shown), but in natural oceans, lakes, rivers, etc., the housing 1 will be arranged near the water surface 8A.

[0048] The housing 1 has a non-flow region (shown by a solid line in Fig. 1) that makes the whole liquid and gas impermeable to permeation and flow, except for a part of the portion close to the water surface 8A of the aqueous solution 9. It has a gas flow region 2 (shown by a dashed-dotted line in Fig. 1) that allows at least the permeation and flow of hydrogen gas and makes the permeation and flow of liquid impossible in a part of the portion close to the water surface 8A. Three measurement parts (acquisition parts) are arranged in the housing 1. That is, a hydrogen gas partial pressure measurement part 4 for acquiring the hydrogen gas partial pressure of the gas 3A in the internal space 3 of the housing 1, a temperature measurement part 5 for acquiring the temperature of the gas 3A in the internal space 3 of the housing 1, and a pH measurement part (also called a pH meter) 6 for measuring the pH of the aqueous solution 9 are arranged in the housing 1. The hydrogen gas partial pressure measurement part 4 measures the hydrogen gas index pH2 and the hydrogen electrode potential of the aqueous solution by being arranged in the gas phase in equilibrium with the aqueous solution. As the hydrogen gas partial pressure measurement part 4, for example, a semiconductor type hydrogen concentration meter can be used, which detects the change in the electrical resistance value generated when the heated metal oxide semiconductor contacts hydrogen gas as the hydrogen gas concentration. For example, SG8541 of Riken Keiki Co., Ltd. can be used. The hydrogen gas partial pressure can be obtained by multiplying the measured hydrogen concentration by 1 atmospheric pressure (10 5 Pa).

[0049] Note that the sensor part at the lower tip of the pH measurement part 6 in the figure is inserted into the aqueous solution 9. That is, in the case of Fig. 1, only the tip sensor part of the pH measurement part 6 is immersed in the aqueous solution 9, and the part of the housing 1 close to the water surface 8A is above the water surface 8A and is not immersed in the aqueous solution 9. With this configuration, the gas 3A in equilibrium with the aqueous solution 9 flows into the internal space 3 of the housing 1 through the gas flow region 2. Note that the gas flow region 2 can be composed of an opening provided at the lower part of the housing 1 or a membrane that allows at least the permeation and flow of the gas 3A containing hydrogen gas. Therefore, the hydrogen gas partial pressure and temperature of the gas 3A in equilibrium with the aqueous solution 9 are acquired and measured by the hydrogen gas partial pressure measurement part 4 and the temperature measurement part 5, respectively.

[0050] The output signals of the hydrogen gas partial pressure measurement unit 4, the temperature measurement unit 5, and the pH measurement unit 6 are respectively supplied to the arithmetic and control unit 24 of the hydrogen electrode potential measurement device described later via the corresponding interfaces 4A, 5A, and 6A. A housing 1 formed from a non-flow area that prevents the flow of liquid, a gas flow area 2 that allows at least the flow of hydrogen gas, a hydrogen partial pressure measurement unit 4 that measures the hydrogen partial pressure of the gas 3A in the space 3 inside the housing 1, a temperature measurement unit 5 that measures the temperature of the gas 3A to be measured, a pH measurement unit 6 that measures the pH of the aqueous solution 9, and interfaces 4A, 5A, and 6A as means for respectively outputting information on the hydrogen gas partial pressure, temperature, and pH are provided. The position of the water surface 8 of the aqueous solution 9 and the measurement device is shown.

[0051] In a closed space, when the gas 3A and the aqueous solution 9 are in an equilibrium state, the pH measurement unit 6 is immersed in the aqueous solution 9 beyond the water surface 8 of the aqueous solution 9. The gas 3 in equilibrium with the aqueous solution 9 is measured by the hydrogen gas partial pressure measurement unit 4 through the opening of the gas flow area 2 or a membrane permeable to the gas 3.

[0052] FIG. 2 is a schematic diagram showing a preferred embodiment of a temperature / hydrogen gas partial pressure / pH measurement unit 20B that constitutes a part of an apparatus for obtaining the redox state of an aqueous solution of the present invention by using the hydrogen electrode potential as the redox state of the aqueous solution of the present invention. It is a schematic diagram showing what is used in an open space when the gas 3B in contact with the aqueous solution 9 to be measured is not in an equilibrium state with the aqueous solution 9. In FIG. 2, elements identical or corresponding to those in FIG. 1 are denoted by the same reference numerals, and their descriptions are omitted. Among the configurations in FIG. 2, parts different from those in FIG. 1 will be described. In FIG. 2, a part of the lower part of the housing 1 in the figure is immersed in the aqueous solution 9. At this time, at least the gas flow region 2 is immersed in the aqueous solution 9, and the aqueous solution 9 and the closed space in the housing 1 are installed in the aqueous solution 9 so as to be interposed with the gas flow region 2 therebetween. The gas 3B in the closed space 3 in the housing 1 surrounded by the non-flow part reaches an equilibrium state with the aqueous solution 9 through the gas flow region 2. The hydrogen gas partial pressure of this equilibrium state gas 3B is measured by the hydrogen gas partial pressure measurement unit 4. In realizing the temperature / hydrogen gas partial pressure / pH measurement unit 20B, a standby time for the space 3 in the housing 1 in FIG. 1 to reach an equilibrium state with hydrogen in the aqueous solution 9 is set in advance. The diffusion time of hydrogen is defined by the size of the space in the housing 1 and the size of the gas flow region 2. In FIG. 2, the gas flow region 2 is the time for diffusion through the opening or the membrane permeable to the gas 3B.

[0053] In an open space, when the gas 3B and the aqueous solution are not in an equilibrium state, the gas flow region 2 including the non-flow part of the housing 1 through which the gas 3B and the liquid do not pass is immersed in the aqueous solution 9 beyond the water surface 8 of the aqueous solution 9. The pH meter 6 is immersed in the aqueous solution 9. At this time, at least the gas flow region 2 is immersed in the aqueous solution 9, and the aqueous solution 9 and the closed space in the housing 1 are installed in the aqueous solution 9 so as to be interposed with the gas flow region 2 therebetween. The gas 3B in the closed space in the housing 1 surrounded by the non-flow part reaches an equilibrium state with the aqueous solution 9 through the gas flow region 2, the opening, or the membrane through which the gas 3B passes. The hydrogen gas partial pressure of this equilibrium state gas 3B is measured by the hydrogen gas partial pressure measurement unit 4.

[0054] FIG. 3 is a schematic diagram showing a preferred embodiment of a temperature / hydrogen gas partial pressure / pH measurement unit 20C that constitutes a part of an apparatus for obtaining the redox state of an aqueous solution 9 of the present invention by executing a method for obtaining the redox state of the aqueous solution of the present invention as a hydrogen electrode potential. The gas 3B in contact with the aqueous solution 9 to be measured and the aqueous solution 9 is a gas 3B having a known hydrogen partial pressure, and is a schematic diagram showing the case where they are mixed in a sealed container to reach an equilibrium state. In FIG. 3, the same or corresponding elements as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. Among the configurations of FIG. 3, the parts different from those of FIG. 1 will be described.

[0055] A part of the aqueous solution 9 and the gas 3 having a known hydrogen gas partial pressure are mixed in a sealed container 10, and the effective hydrogen gas partial pressure of the gas 3B in an equilibrium state is measured. At this time, at least the gas flow region 2 is immersed in the aqueous solution 9, and is installed in the aqueous solution 9 so that the aqueous solution 9 and the closed space 3 in the housing 1 can be interposed with the gas flow region 2 therebetween. The gas 3B in the closed space 3 of the housing 1 surrounded by the non-flowing part reaches an equilibrium state with the aqueous solution 9 through the gas flow region 2, the opening, or the membrane 8 through which the gas 3B passes. The gas 3B in this equilibrium state is measured by the hydrogen gas partial pressure measurement unit 4.

[0056] In the implementation of the temperature / hydrogen gas partial pressure / pH measurement units 20A, 20B, and 20C, a standby time for the space 3 in the housing 1 in FIGS. 1 to 3 to reach an equilibrium state with hydrogen in the aqueous solution 9 is set in advance. The diffusion time of hydrogen is defined by the size of the space 3 in the housing 1 and the size of the gas flow region 2. In FIG. 1, the gas flow region 2 is the time for diffusion through the opening or the membrane permeating the gas 3A. In FIG. 2, the gas flow region 2 is the time for diffusion through the membrane permeating the gas 3B.

[0057] FIG. 4 is a block diagram showing a preferred embodiment of a hydrogen electrode potential measurement apparatus for an aqueous solution of the present invention. A preferred embodiment of the method for measuring the hydrogen electrode potential of the aqueous solution of the present invention will also be described with reference to FIG. 4. The temperature / hydrogen gas partial pressure / pH measurement units 20A, 20B, and 20C shown in FIGS. 1 to 3 are denoted by the reference numeral 20 in FIG. 4. In other words, depending on the measurement situation, one of the arrangements in FIGS. 1 to 3 is selected.

[0058] In the present invention, the hydrogen electrode potential of the aqueous solution 9 is measured. However, for example, in an aqueous solution used in a chemical reaction, a culture solution used for a living organism, river water or seawater in nature, it is difficult to directly measure the hydrogen gas partial pressure due to solubility relationships. Therefore, in the present invention, the hydrogen partial pressure of the gas phase in equilibrium with the aqueous solution is used. The hydrogen gas partial pressure measuring unit 4 measures the hydrogen gas index pH2 and the hydrogen electrode potential of the aqueous solution 9 by being arranged in the gas phase in equilibrium with the aqueous solution 9. As the hydrogen gas partial pressure measuring unit 4, in addition to the aforementioned device, for example, a Clark electrode type hydrogen gas concentration meter that uses catalytic platinum with a membrane to detect the change in current due to voltage as the dissolved hydrogen gas concentration, for example, the hydrogen microsensor of Unisense (Denmark), a micromanipulator, and a microsensor multimeter can be used. The hydrogen gas partial pressure in the equilibrium state can be obtained by dividing the measured dissolved hydrogen gas concentration by the saturated dissolved hydrogen gas concentration defined by the temperature. The output signals of the temperature, hydrogen gas partial pressure, and pH measuring unit 20 indicate the measured hydrogen gas partial pressure, temperature, and pH, and are sent to the arithmetic and control unit 24. In the storage unit 26, a predetermined arithmetic formula is stored in advance, and the arithmetic result in the arithmetic and control unit 24 is stored as needed. The input unit 22 gives an instruction to start arithmetic operations to the arithmetic and control unit 24 and is used to set the value of the hydrogen ion index pH, which will be described later, to the arithmetic and control unit 24.

[0059] The hydrogen electrode potential of the aqueous solution obtained by calculation in the calculation and control unit 24 is sent to the display unit 28 and displayed as a numerical value. The input unit 22, the calculation and control unit 24, the storage unit 26, and the display unit 28 can also be configured by a personal computer keyboard and mouse, a central processing unit (CPU), a memory (RAM, ROM), and a display. In this case, in order to supply the temperature, the hydrogen gas partial pressure, and the output signal of the pH measurement unit 20 to the USB input unit of the personal computer in an appropriate format, the above-described interfaces 4A, 5A, and 6A are used as necessary. In addition to displaying the hydrogen electrode potential of the aqueous solution, the display unit 28 can also display the calculated hydrogen gas index pH2, the measured temperature, and pH. In addition to the above calculations, the calculation and control unit 24 can control the storage unit 26 and the display unit 28 according to an instruction from the operator of the device input by the input unit 22.

[0060] In the storage unit 26, an arithmetic expression for calculating the hydrogen electrode potential Eh of the aqueous solution is stored in advance. The basis of the arithmetic expression is

Number

[0061] is. For example, when the temperature T is 25 °C (298.15 K), the hydrogen electrode potential is Eh = 0.0296×pH 2 -0.0592×pH (V). Here, since the pH of the aqueous solution is measured simultaneously as described above, an appropriate value can be input to the calculation unit by the input unit 22. On the other hand, since the change range of pH is small in the pH buffer solution, this can be fixed to, for example, 7.0. Therefore, the input unit 22 can input 7.0 as pH, store this 7.0 in the storage unit 26 in advance, and use it. However, 7.0 is already incorporated as pH, and the above basic arithmetic expression is

Number

[0062] The hydrogen electrode potential of the aqueous solution obtained by arithmetic in the arithmetic and control unit 24 is sent to the display unit 28 and displayed as a numerical value. In addition to displaying the hydrogen electrode potential of the above aqueous solution, the display unit 28 can also display the calculated hydrogen gas exponent pH2, the measured temperature, and pH. Incidentally, in addition to the above arithmetic, the arithmetic and control unit 24 can control the memory unit 26 and the display unit 28 according to an instruction from the operator of the device input by the input unit 22.

[0063] As another method, an arithmetic formula for calculating the hydrogen electrode potential E of an aqueous solution is stored in advance in the memory unit 26. When directly measuring the dissolved hydrogen concentration, the hydrogen gas partial pressure is obtained from the dissolved hydrogen concentration according to Henry's law. For example, when the temperature is 25 °C and the atmospheric pressure is 1 bar (atm), the saturated hydrogen concentration is 1.6 ppm. Therefore, the basis of the arithmetic formula is the hydrogen gas partial pressure [Number] (bar)

[0064] is obtained. Also, a part of the aqueous solution is mixed with a gas having a known hydrogen gas partial pressure in a sealed container, and the effective hydrogen gas partial pressure Px of the gas in the equilibrium state is measured. At this time, the hydrogen partial pressure P X in the aqueous solution is measured from the hydrogen partial pressure P H2 in the sealed container. When the temperature T (K) of the sealed container and the aqueous solution is set, the hydrogen gas partial pressure P A in the container before adding the aqueous solution is set, the volume of the gas phase in the sealed container is V A is set, and the volume of the liquid phase is V S is set. Since the number of moles of the gas before and after the equilibrium state is equal, using the gas constant R, the basic formula of the arithmetic expression is

Equation

[0065] Next, the above simplification can be used to calculate the variation of the hydrogen electrode potential. For example, when the pH is constant, the variation ΔEh of the hydrogen electrode potential is from the change ΔpH 2 of the hydrogen gas index pH 2 as

Equation

[0066] is obtained. When the temperature is 25 °C (298.15 K), the variation of the hydrogen electrode potential is

Equation

[0067] In a preferred embodiment of the measuring device, when the aqueous solution to be measured is in a closed space, since hydrogen gas is in an equilibrium state between the gas phase and the liquid phase, the hydrogen partial pressure, temperature, and pH of the aqueous solution in the gas phase within the closed space are measured. The gas 3A in the closed space is in equilibrium with the liquid, and the hydrogen gas partial pressure in the gas phase is measured. Next, in the case of an aqueous solution in an open space, since hydrogen gas is not in an equilibrium state between the gas phase and the liquid phase, the measuring device is immersed partially or entirely in the liquid so that the inside of the device is in an equilibrium state with the liquid. The hydrogen partial pressure of the gas 3B inside the device is measured. Also, the temperature of the gas phase and the pH of the aqueous solution are measured. Further, when the measuring device cannot be immersed in the aqueous solution, the aqueous solution is collected in another container, and the hydrogen partial pressure of the gas phase that has come into equilibrium with the enclosed gas 3B is measured at the same temperature as the aqueous solution. The temperature and pH of the aqueous solution are measured simultaneously.

[0068] Next, a preferred form of the system used in the method for verifying the hydrogen electrode potential obtained by the hydrogen electrode potential acquisition method and device of the present invention will be described. FIG. 4 is a block diagram showing a preferred form of the method used in the method for verifying the hydrogen electrode potential obtained by the hydrogen electrode potential acquisition method and device for an aqueous solution of the present invention. This system includes a medical oxygen source 30, a hydrogen-oxygen gas supply source 32, a flow meter 34, a switching valve 38, a bubbling device 40, a thermometer, a pH and potential measuring device 46 provided in a container 41 constituting the bubbling device 40, an interface 50, a display 52, and a storage unit 54. The bubbling device 40 can utilize what is generally used as an air humidifier, guides the gas supplied from the outside through a conduit 42 into the container 41, causes the introduced gas to bubble (be vaporized) in the liquid in the container 41, and discharges it to the outside through a discharge pipe 44 from the upper space of the container 41.

[0069] The medical oxygen source 30 delivers oxygen that has been depressurized from a medical oxygen cylinder. The oxygen-hydrogen gas supply source 32 delivers a mixed gas containing 0.5 l of oxygen and 1.0 L of hydrogen per minute. The depressurized medical oxygen delivered from the medical oxygen source 30 and the mixed gas containing oxygen and hydrogen delivered from the oxygen-hydrogen gas supply source 32 are supplied to the bubbling device 40 through the flow meter 34, with either one selected by the switching valve 38. The bubbling device 40 is generally used as an air humidifier, and a phosphate buffer solution (10 mM, pH 7.1) 56 can be placed in the container 41 that constitutes it. As such a phosphate buffer solution, for example, PBS(-) 166-23555 manufactured by Fujifilm Wako Pure Chemical Corporation can be used. A preferred embodiment of the method for verifying the hydrogen electrode potential of the aqueous solution of the present invention will be described with reference to FIG. 2.

[0070] A phosphate buffer solution (10 mM, pH 7.1) 56 is placed in the container 41 that constitutes the bubbling device 40. The temperature, pH, and oxidation-reduction potential ORP of the phosphate buffer solution in the container 41 are measured by the pH and oxidation-reduction potential measuring device 46. As the temperature, pH, and oxidation-reduction potential measuring device 46, for example, pH6600 and ORP-6600S manufactured by Custom Co., Ltd. can be used. The output signal of the temperature, pH, and oxidation-reduction potential measuring device 46 is given to the display unit 52 and the storage unit 54 through the signal transmission path 48 and the interface 50. When the pH and reduction potential are measured and stored in the storage unit 44, the switching valve 38 is operated to supply medical oxygen to the bubbling device 40 at a first predetermined flow rate for a first predetermined time. Here, the first predetermined flow rate is 0.5 L / min, and the first predetermined time is 1 hour. As the medical oxygen, for example, medical oxygen manufactured by Air Water can be used.

[0071] After the supply of air stops at the first predetermined time, the temperature, pH, and oxidation-reduction potential ORP of the phosphate buffer solution in the container 41 are measured again with the pH and reduction potential measuring device 46, and the measured potential is stored in the storage unit 54. Next, the oxidation-reduction potential ORP measured after the supply of medical oxygen is corrected by the oxidation-reduction potential ORP measured before the supply of medical oxygen. For example, if the oxidation-reduction potential ORP measured before the supply of medical air is 310 mV, this potential will be taken as the reference 0 mV. That is, if the oxidation-reduction potential ORP measured after the supply of medical air is 305 mV, subtract 310 mV from this value to make the change in the hydrogen electrode potential -5 mV.

[0072] Drain the phosphate buffer solution in the container 41 and put a new phosphate buffer solution into the container 41. Measure the temperature, pH, and oxidation-reduction potential ORP of the new phosphate buffer solution in the container 41 in the same manner as described above. After the measurement and storage of the measured values are completed, supply an oxygen-hydrogen mixed gas containing hydrogen at a predetermined concentration to the bubbling device 40 at a second predetermined flow rate for a second predetermined time. Here, the second predetermined flow rate is 1.5 L / min, and the second predetermined time is 1 hour. Also, the predetermined concentration is, for example, 66%, and for example, a hydrogen supply device Helix beta EH90 can be used.

[0073] After the supply of the second predetermined time ends, measure and store the temperature, pH, and oxidation-reduction potential ORP of the new phosphate buffer solution in the container 41 again with the pH and potential measuring device 46. Correct the oxidation-reduction potential ORP measured after the supply of the oxygen-hydrogen mixed gas by the oxidation-reduction potential ORP measured before the supply of the oxygen-hydrogen mixed gas. If the measured potential here is -161 mV, subtract 41 mV as described above to make the change in the hydrogen electrode potential -202 mV.

[0074] Using the two oxidation-reduction potentials ORP obtained in this way, before bubbling with medical oxygen and the oxygen-hydrogen mixed gas, the pH 2 is 6.2, and when it is after bubbling with the oxygen-hydrogen gas containing hydrogen at a predetermined concentration, the pH 2 is 0.18, and the pH 2Grasp the change pattern of the oxidation-reduction potential ORP with respect to the change of 2 When the pH is 6.2, the oxidation-reduction potential ORP is +41 mV. After bubbling, the pH 2 When it is 6.2, the oxidation-reduction potential ORP is -161 mV. Therefore, the graph in Figure 4 is created by the line segment connecting these points. In the case of medical oxygen, the oxidation-reduction potential did not change due to bubbling, while in the oxygen-hydrogen mixed gas, the oxidation-reduction potential decreased (medical oxygen; -5.2 ± 3.4 mV, oxygen-hydrogen mixed gas; -203 ± 21 mV, p = 0.002). There was no significant difference in the change of pH before and after bubbling oxygen. When the oxygen-hydrogen mixed gas (10 Pa) was bubbled, the pH changed from 7.06 to 7.16 before and after bubbling. One of the influencing factors for pH measurement is log[hydrogen gas partial pressure (Pa) / 100 kPa], as described in the definition of pH in the United States: Measurement of pH. Definition, Standards, and Procedures. Pure Appl. Chem. 74, 2169-2200 (2002).

[0075] To create the graph in Figure 4 by the above measurement, in order to reduce the measurement error, the measurement of the above potential was performed multiple times (for example, 3 times or more), and the average value of the measurement results was used. In the graph of the oxidation-reduction potential ORP before and after hydrogen gas bubbling in Figure 6, the pH 2 When it is 6.2, the oxidation-reduction potential and the pH 2 When it is 0.18, the line segments extending above and below the points indicating the oxidation-reduction potential respectively show the standard deviation. The oxidation-reduction potential ORP changed due to the bubbling of the oxygen-hydrogen mixed gas, and this change approximated the change of the hydrogen electrode potential using the Nernst equation. Since the hydrogen gas concentration in the oxygen-hydrogen mixed gas increased from 0.6 ppm in the atmosphere before air supply to 1.0 / (0.5 + 1.0) = 0.66, the hydrogen gas partial pressure changed from 0.6×10 -6 bar to 0.66 bar. The antilogarithm of the hydrogen gas partial pressure is pH2 =-log(0.6×10 -6 ) = 6.22, the pH changes from 2 =-log(66×10 -2 ) to 0.18. Therefore, the approximate formula:

Number

[0076] The change in the redox potential according to

Number

[0077] becomes

Number

[0078] and it can be confirmed that it approximates the change in the measured value

Industrial Applicability

[0079] The present invention can be used in the liquor brewing industry, nutrition research field, food processing industry, agriculture, pharmaceutical development and manufacturing industry, medical industry, etc. Both the conventional relative hydrogen score rH and the present invention are effective for managing the brewing processes of wine, beer, sake, etc. Also, both the conventional relative hydrogen score rH and the present invention are effective as means for evaluating the redox state (e.g., antioxidant state and possibility of spoilage) of fruit juices, etc. in nutritional antioxidant research and the food processing industry. Further, both the conventional relative hydrogen score rH and the present invention are useful for inorganic chemistry of metals (oxidation and reduction), biochemistry of oxidation or reduction of metals, organic agriculture, measurement and formulation of soil nutrients in the gardening area, environmental drainage and restoration research, research on groundwater including analysis of surface water, underground aquifers, water from deep wells, etc., and seawater management in aquariums. Furthermore, since the present invention directly measures the hydrogen partial pressure, more effective utilization of the hydrogen electrode potential can be expected compared to the relative hydrogen score.

[0080] For example, in organic electrochemistry, constant potential electrolysis is suitable for high selectivity in organic electrosynthesis. Generally, the electrode reactions of organic compounds are complex, and it is not uncommon to obtain multiple products. When the electrolytic reduction of aromatic carbonyl compounds is carried out under acidic conditions, products such as alcohol forms and pinacol forms are obtained simultaneously. The limiting current at this time has two stages. When selectively obtaining the pinacol form, constant potential electrolysis may be carried out in the potential range corresponding to this limiting current. That is, appropriate reaction conditions can be obtained by measuring the hydrogen electrode potential of the aqueous solution, not only the dissolved oxygen concentration (DO) and hydrogen ion concentration (pH).

[0081] Furthermore, in biochemistry and medical science, all energy generation in organisms requires redox reactions by the electron transport system. Energy is obtained from the decomposition of glucose using nicotinamide adenine dinucleotide (NADH) etc. as electron donors. In anaerobic respiration and fermentation, the potential difference with the final electron acceptor such as alcohol is small, and the balance of the redox reaction of NAD + / NADH is strongly affected by the fluctuation of the hydrogen electrode potential. Both the relative hydrogen score rH of the prior art and the present invention are useful.

[0082] In aerobic respiration, since oxygen is used as the final electron acceptor, the redox potential of NAD + / NADH and the redox potential of H 2 O / O 2 The difference in redox potential is large and the reaction rate is oxygen-dependent. However, even in aerobic respiration, when the diffusion ability of oxygen is exceeded, a relatively hypoxic state occurs. In a relatively hypoxic state, since the potential difference between NAD + / NADH and H 2 O / O 2 becomes small, the fluctuation of the redox potential of NAD + / NADH will greatly affect the rate of aerobic respiration. Even in aerobic respiration, the hydrogen electrode potential of the aqueous solution is NAD +It affects the balance of the oxidation-reduction reaction of / NADH. Both the relative hydrogen score rH of the prior art and the present invention are useful. Therefore, biological oxidation-reduction reactions can be utilized in various industries by seeking optimal conditions based on the hydrogen electrode potential in addition to dissolved oxygen and pH.

Explanation of Signs

[0083] 1 Housing formed from a non-flow area that prevents the flow of liquids and gases 2 Flow area of the housing that allows at least the flow of hydrogen gas 3 Space inside the housing 3A, 3B Gases inside the housing 4 Hydrogen partial pressure measurement unit 4A, 5A, 6A Interface 5 Temperature measurement unit 6 pH measurement unit 7 Output means for hydrogen partial pressure, temperature, and pH 8 Water surface of the aqueous solution 9 Aqueous solution 10 Sealed container formed from a non-flow area that prevents the flow of liquids and gases 20, 20A, 20B, 20C Temperature, hydrogen gas partial pressure, pH measurement unit 22 Input unit 24 Arithmetic and control unit 26 Recording unit 28 Display unit 30 Medical oxygen source 32 Oxygen-hydrogen mixed gas generator 34 Flow meter 38 Switching valve 40 Bubbling device 41 Container 42 Conduit 44 Discharge pipe 46 pH and potential measurement device 48 Signal transmission path 50 Interface (I / F) 52 Display unit 54 Storage unit 56 Phosphate buffer solution

Claims

1. Obtaining the effective hydrogen gas partial pressure of the gas phase in equilibrium with the aqueous solution; Obtaining the temperature of the gas phase; Obtaining the hydrogen ion activity (pH) of the aqueous solution; The step of calculating the inverse logarithm (pH 2 ) of the voltage division, and Using the temperature, the hydrogen ion activity (pH), and the antilogarithm (pH 2 ), analyzing the hydrogen electrode potential of the aqueous solution; A method for obtaining the redox state of an aqueous solution having the above as the hydrogen electrode potential.

2. Hydrogen gas index pH 2 is the negative logarithm (pH 2 = -log[hydrogen gas partial pressure (Pa) / 100 kPa]) of the effective hydrogen gas partial pressure as defined, and the operation of the hydrogen gas index pH 2 is performed according to a predetermined arithmetic formula stored in the storage means: 【Number 28】 Read it, calculate the hydrogen electrode potential by the predetermined arithmetic expression, and the obtained hydrogen electrode potential and pH 2 A method for obtaining the redox state of an aqueous solution according to claim 1, comprising the step of displaying.

3. The step of displaying the change in the hydrogen electrode potential as a change in the hydrogen gas index pH 2 is provided. A method for obtaining the redox state of the aqueous solution according to Claim 2 as the hydrogen electrode potential.

4. In a state where the hydrogen ion activity (pH) is buffered or there is no change in the hydrogen ion activity (pH), the change ΔEh in the hydrogen electrode potential as the change in the redox state of the aqueous solution is represented by the following arithmetic expression using the change ΔpH in the inverse logarithm (pH 2 ): 2 ​ 【Number 29】 Calculating by; The change in the hydrogen electrode potential obtained by the above calculation 【30 numbers】 Displaying; A method for obtaining the redox state of the aqueous solution according to Claim 1 as the hydrogen electrode potential, having the above steps.

5. Measuring the effective hydrogen gas partial pressure of the gas in equilibrium by mixing a part of the aqueous solution and a gas with a known hydrogen gas partial pressure in a sealed container; Calculating the effective hydrogen partial pressure of the aqueous solution from the hydrogen partial pressure of the gas in the sealed container; A method for obtaining the effective hydrogen gas partial pressure of an aqueous solution having the above steps.

6. Measuring the concentration of dissolved hydrogen gas in the aqueous solution; Calculating the effective hydrogen gas partial pressure of the gas phase in equilibrium with the aqueous solution using the solubility of the dissolved hydrogen gas obtained from the concentration of the dissolved hydrogen gas and Henry's constant; A method for obtaining the effective hydrogen gas partial pressure of an aqueous solution having the above steps.

7. A hydrogen gas partial pressure acquisition unit for obtaining the hydrogen gas partial pressure of the gas phase in equilibrium with the aqueous solution; A temperature acquisition unit for obtaining the temperature of the gas phase; A hydrogen ion activity (pH) acquisition unit for obtaining the hydrogen ion activity (pH) of the aqueous solution; The negative logarithm (pH 2 ) of the hydrogen gas partial pressure is calculated, and the hydrogen gas index pH 2 defined by the negative logarithm (pH 2 ), a temperature, and the hydrogen ion activity (pH) to analyze the hydrogen electrode potential of the aqueous solution, and an arithmetic unit An apparatus for obtaining the redox state of an aqueous solution having the above as the hydrogen electrode potential.

8. The apparatus for obtaining the redox state of the aqueous solution according to Claim 7, wherein the hydrogen gas partial pressure acquisition unit, the temperature acquisition unit, and the hydrogen ion activity (pH) acquisition unit are attached to form a non-flow region that prevents the flow of liquid and gas, and has a housing having a flow region or a membrane that allows at least the flow of hydrogen gas.

9. Hydrogen gas index pH 2 is the negative logarithm (pH 2 = -log[hydrogen gas partial pressure (Pa) / 100 kPa]) when defined as such, and the operation of the hydrogen gas index pH 2 is performed according to a predetermined arithmetic expression stored in the storage means: 【Number 31】 Reading and calculating the hydrogen electrode potential by the predetermined calculation formula; means for displaying the obtained hydrogen electrode potential and pH 2 and means for displaying An apparatus for obtaining the redox state of the aqueous solution according to Claim 8, having the above means.

Images