JPH03216544A - Method and apparatus for measuring concentration of hydrogen peroxide - Google Patents

Abstract

PURPOSE:To enhance measuring accuracy by continuously titrating a solution to be measured with KMnO4 by a fixed quantity per a unit time and measuring the concn. of H2O2 from the time required till the end point of reaction. CONSTITUTION:A KMnO4 pump 5 is turned ON to supply KMnO4 to a reaction tank 1 from a storage tank 4 in a fixed quantity per a unit time and turned OFF when the ORP value due to an ORP electrode 13 reaches the end point of reaction. Next, the concn. of H2O2 is calculated from the time required until the ORP value reaches the end point of reaction according to a predetermined operation formula. By determining the supply quantity of KMnO4 per a unit time as mentioned above, the clocking of a titration time, that is, the supply quantity of KMnO4 can be set and, by determining the supply quantity of KMnO4 per a unit time to a little, measuring accuracy can be easily enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention involves titrating an aqueous solution containing hydrogen peroxide (H to z) with potassium permanganate (KMnO,) and using an ORP electrode immersed in the aqueous solution. The present invention relates to a hydrogen peroxide concentration measuring method for detecting the end point of a redox reaction between H,02 and KMn04 from a change in the detected ORP value, and a measuring device used therefor.

[Prior Art] H,02 is used in various ways, for example, as a bleaching agent or as a chemical agent for copper etc., but whether it is used as a bleaching agent or as an etching agent, H,O, Containing aqueous solution? 20. It is necessary to keep the concentration constant. Therefore, the H20 concentration of the aqueous solution is measured, and if the concentration is lower than a preset standard value, the H20 concentration is measured.
A pure solution of No. 202 is added to the aqueous solution to maintain the concentration.

By the way, are there any known methods for measuring the concentration of ■,02 such as volumetric analysis, colorimetric analysis, ORP analysis?
P analysis method is relatively often used. The ORP analysis method is based on the fact that when KMnO4 is added to an aqueous solution containing H20, the oxidizing agent H,0 becomes a reducing agent, similar to the original KMnO4, and an oxidation-reduction reaction occurs, causing a rapid change in the ORP value at the end of the reaction. The end point of the reaction is detected using the method, and H, O,
This method measures the concentration of And conventionally, O
The RP analysis method uses a weighing mass or a tube pump to
In many cases, a method of titrating M n 0 4 was adopted.

By the way, in the past, KMnO4 was supplied using a measuring mass or a tube pump, and depending on how much KMnO was supplied until the end of the reaction, That is, the concentration of I{,O, was measured based on the amount of KMn04 supplied, but the accuracy was not necessarily high. Because KMnO. This is because the accuracy is determined by the capacity of the measuring mass and the flow rate of the tube pump.

That is, using a weighing mass, KMnO. When titration is performed, K M n O supplied by one feeding operation is
The amount a is determined by the volume of the weighing mass, and this amount is approximately constant. Then, it is determined how many times the metering mass has been supplied, and the titration amount is the product of the number of times the metering mass has been supplied and the volume of the metering mass. Therefore, the measurement accuracy of H20 and concentration is determined by the volume of the weighing mass, making it difficult to improve the measurement accuracy. Furthermore, there is some variation in the amount of KMnO supplied by one supply operation of the weighing mass, which also causes a decrease in measurement accuracy.

Furthermore, when titrating KMnOa using a tube pump, contact between the tube and the roller may cause the tube to deteriorate and the flow rate to become unstable, making it necessary to constantly change the contact surface in order to improve the stability of the flow rate. There is a problem that it is not desirable.

Furthermore, analysis is performed to calibrate the variation in measured values caused by unstable flow rates, in other words, the H202 concentration is calculated by comparing the analytical value of a standard solution, which is a sample with a known H202 concentration, and the analytical value of the measured value. The reality is that it was necessary to perform the operation for each measurement.

The present invention has been made to solve these problems, and its purpose is to improve measurement accuracy.

]Configuration of the Invention In order to achieve the above object, the present invention
is continuously titrated into the liquid to be measured at a constant rate per unit time.
This method is characterized in that the concentration of H202 is measured from the time required to reach the end point.

, Effect] According to the present invention, KMnO. The concentration of H,0, is measured by continuously titrating a fixed amount of H,0, per unit time into the aqueous solution to be measured, and measuring the time taken to reach the end point.The supply amount of KM n04 per unit time is determined. The titration time can be measured by keeping the KMnO. This makes it possible to control the concentration of H,0, on a time axis. By setting a small supply amount of KMnO per unit time, measurement accuracy can be easily increased. Therefore, the concentration of H 2 O 2 can be controlled on a time axis with high precision.

[Example 1 Hereinafter, the present invention will be explained in detail according to illustrated embodiments.

1 to 4 show an embodiment of the H, O, and concentration measuring device of the present invention, and FIG. 1 is a block diagram showing the overall structure of the device.

In the drawing, 1 is a funnel-shaped reaction tank, 2 is a tank for storing water for washing, and 3 is a pump. The pump 3 supplies water to the reaction tank 1 for washing. 4 is KMn
O. A tank 5 for storing KMnO.
6 is a tank for sampling liquid, 7 is a tank for storing pure liquid of H20 for replenishment, 8 is a pump for supplying H20 to the reaction ml.
is a pump that supplies H,0, in the tank 7 to the tank 6, 9 is a pump that supplies the sampling liquid from the tank 6 to the reaction tank 1, and 10 is a sulfuric acid H2SO. The tank 11 for storing sulfuric acid is a pump that supplies the sulfuric acid in the tank 10 into the reaction tank 1.

A diaphragm pump is used for each of the pumps 3, 5, 8, 9, and 11 mentioned above. In other words, in tube pumps that are often used in conventional automatic analyzers R, tube deterioration occurs due to contact with rollers, making the flow rate unstable, and the contact surface must be constantly changed to improve the stability of the flow rate. There is a problem that it is necessary and undesirable for work. In addition, plunger pumps were often used, but although plunger bombs have a high flow rate stability, they are very expensive. However, the flow stability of the Dia7 ram pump is much better than that of the tube pump, and only slightly worse than that of the plunger pump. Therefore, sufficient analytical precision can be obtained and the price is low. Therefore, 7
A ram pump was used.

12, 12, 12 are check valves provided at the ends of hoses that lead the liquid from the pumps 5, 9, 1l to the reaction tank 1. These check valves 12, 12, and 12 are for preventing the liquid from flowing backward when the analysis is stopped, and can prevent the accuracy of the next measurement from lowering due to the backflow of the liquid. 13 is an ORP electrode, which uses a low-sensitivity type electrode for fermentation to obtain a smooth titration curve. Specifically, platinum is used as an electrode. A low sensitivity one is used for a high sensitivity OR.
This is because if a P electrode is used, it will be susceptible to the influence of KMnO, and the analysis values will vary widely, making it impossible to accurately detect the end point.

14 is a stirring rod, which is rotated by a motor 15. FIGS. 2A and 2B are perspective views showing different examples of the stirring rod l4. The stirring rod I4 is provided with a stirring part 16 at the lower end, and it is preferable that the stirring part 16 be made into a flat plate shape as shown in the figure (A), or a cylindrical shape as shown in the figure (B). . Conventionally, propellers were used for stirring, but
When a groper is used, there is a problem in that a large amount of foam is generated. This is because the flat or cylindrical stirring part I6 generates less bubbles. 17 is H,
02 This is a controller to keep the concentration constant.

Figure 3 shows the stirring rod, ORP electrode, and KMnO dropping positions.
FIG. 4 is a plan view showing the planar positional relationship between the dripping position of washing water, the dripping position of sulfuric acid as a diluent, and the dripping position of a sampling aqueous solution. It is a sectional view showing an RP electrode and a stirring bar.

An ORP electrode 13 is placed along the stirring direction around the reaction tank 1,
KMnO4 dropping position, cleaning water dropping position, H, So
4 dropping positions are placed at the dropping position of the sampling aqueous solution, and the ORP electrode is placed farthest along the stirring direction from the dropping position of KMnO<. This is an unreacted KM
n0 4 directly touches the ORP electrode and the end point is detected at the ORP″rt!.pole at an earlier timing than originally expected,
H. This is to avoid the o2 concentration being measured too low.

By the way, the liquid volume in the reaction tank L is 50 to 150 milliliters.
The titration rate is 5-20 ml/min, and the sampling volume is 5-20 ml. To set the liquid volume in reaction tank 1 to 50-150 ml, if the liquid volume is equal to or less than that, K M n 0 4 is ORP? T! ．． If the liquid volume exceeds the above range, i.e., 150 ml or more, the stirring efficiency will be low and the degree of dispersion will not be uniform enough, which will also lower the analytical accuracy, which is undesirable. It is from. In addition, the reason for setting the titration rate to 5 to 20 ml/min is that if the titration rate is less than 5 ml/min, the response of the ORP electrode will be delayed and the concentration will be higher than the actual concentration, and if it is more than 20 ml/min, no reaction will occur. KMnO. This is because the concentration may have too strong an influence on the ORP electrode, resulting in the measured concentration being lower than the actual concentration.

In addition, the reason why the sampling amount should be 5 to 20 ml is because if it is less than that, the sampling error will greatly affect the analysis accuracy, and if the sampling amount is more than that, the redox reaction will be too intense. This is because a large amount of gas is generated, and furthermore, this causes problems such as liquid scattering.

The length of the stirring part 16 is half the inner diameter of the reaction tank 1.
The thickness or diameter of the stirring part l6 is 1/2 to 1/20 of the height of the liquid during titration, but under these conditions, no bubbles are generated. This makes it possible to obtain sufficient stirring efficiency. The rotation speed of the stirring rod l4 by the motor 15 is 500 to l20 Orp.
This is because it is possible to obtain sufficient stirring efficiency and to increase the uniform dispersibility of the sampling aqueous solution and K M n O a without generating bubbles.

Note that among these, approximately 800 rpm is optimal.

At Kikoro, we measured the concentration of H,02 using this device,
Furthermore, the insufficient H20 and pure liquid are replenished based on the measurement results, but before explaining these, we will explain the equations for calculating the H20 and D degree, and the H. 0. It is necessary to explain the equation for determining the amount of supply, and I will explain that equation step by step.

(1) H. 0. Relationship between concentration and KMnO consumption amount H,02
and KMnO. reacts as shown below.

2KMnO, +3H, SO. +5H. 0,-+2MnS
O*+K2SO4+8HzO+502 and above 21
1101 K M n 0 4 and 5 mol H 2 0
x force) equivalent. Therefore, KMnO. Since the molecular weight of is 158.0 and the molecular weight of H,0 is 34.0, 316 g of K M n O
, and 170g of 8 2 0 2 are the equivalent weight.

Next, 0.0 when sampling 10 mQ of 35V%Hz02 1v%. IN KMnO, find the consumption amount.

Amount of H,02 in sampling liquid (g) 10mQ x sail01 x 1. l33X O. 35=0
．． 0397(g)0. The concentration of IN KMnO, is 3
．． Since it is 16g/Q, the consumption amount is as follows.

I000 0. lN KMnO. Consumption amount (ml2) = 0.0
738 x 3. ,6-23.35(mQ) As above, HtOx IV%, 10m! Sampling, Q. The end point when titrating with l N K M no 4 is 23.35 ml2, or the OR at this point.
When the P value is captured, the ORI' value is in a stable state, so KMnO. The variation in pump time increases. Therefore, in practical terms, we decided to take 800 mV as the end point, where the change in ORP value is large.

At this time, the titration amount of KMnO was 21. Since OmQ, HioilV% of 0. IN KMnO, the equivalent was set to 21.0 mQ. FIG. 5 is a diagram showing the relationship between titration amount and ORP value.

(2) HzOi Concentration Conversion Formula Since the analysis of H,0,concentration is performed within a 30-minute sequence, the conditions are changed in the following three ways depending on the H,0,concentration to be measured.

] H202 concentration conversion formula 1 for condition ① KMnO. Since the pump flow rate is 10ml2/min, KMnO
, the pump time will be. ('+17+Note H, 02 1V% of ffi
2] Sanda from mi2) Here, KMnOa pump time x SH. Letting O and concentration be W, the following is obtained.

FIG. 6 is a diagram showing the relationship between KMnO, pump on time, and H,0 concentration under condition (2).

1 Hz 0 2 concentration conversion formula for condition (2)] The sampling amount for condition (2) is 1/2 of that of (2), and the concentration of KN n 0 4 is 1/10, so KMnO. The Ponzo time for is as follows.

Here KMnO. Bombing time X s H 2 0 t When the concentration is W, the following equation is obtained.

The 7th x is a relationship diagram between the on time of K M n 0 4 Pong and the H202 concentration under condition (2).

．． H20 of one condition (■), concentration conversion formula 1, sampling amount of condition (■) is 1/2 of ■, K M nO
4 concentrations are the same, so KMnO. The pump time will be:

Here, assuming that the KMn04 bombing time is X%H, O and the concentration is W, the following equation is obtained.

FIG. 8 shows KMnO under condition (2). FIG. 3 is a diagram showing the relationship between pump on time and H202 concentration.

The formulas for the conditions (1) to (2) above are shown below.

The above three equations can be combined into one equation as follows.

×K Mn0 4(N) × 1 0 According to the above formula, under the conditions of ■, ■, ■, K Mn0
It is possible to know the H, 0, concentration from 4 pump hours.

Now, when the H202 concentration of the sampled aqueous solution is measured, if the measured value is lower than the target value, it is a matter of course that the H202 concentration must be replenished. Therefore, in order to maintain the concentration of the insoluble solution at a preset target value (also referred to as a reference value or set value), it is necessary to calculate how much H202 pure liquid should be replenished. Therefore, the target value is set as Z and H. Let us consider how to determine the necessary on-time Y of the replenishment pump of No. 02.

Furthermore, H202? Once the target value Z (V%) of m degrees is set, it is kept constant unless changed.

(3) t'r2oz replenishment pump conversion formula
It is assumed that it is OOQ.

1 condition ■ H x O x pump conversion formula] For example, H2
If 0zlV% is insufficient, add 1000Qxo. ol=10
72 H. O. or be replenished. Therefore, the H202 pump runs for (!QC/4)X60=150 seconds.

On-time of KM n O 4 bomb in 9th or condition ① and H. 2 is a relationship diagram between the H202 concentration and the on time of the H202 pump.

Therefore, the on-time Y of the H202 pump is expressed by the following equation. Note that Z in the formula is }{, O, concentration setting value (reference value). Therefore, H,0,pump time is:

? -Condition ■H, 0 ■Pump conversion formula] For example, H. In case of 0.0.1V% shortage, +000(2
X0.001=112 H202 needs to be replenished. Follow? TeH. O, the pump is (l Q/ 2)X
Must be activated for 60 = 30 seconds.

FIG. 10 is a relationship diagram between the on-time of the K M n O a pump and the H202 concentration, and the on-time of the H20 and pump under condition (2).

Therefore, H20 and pump time are as follows.

60 = 300z-126...Formula■? Case ■ H20, pump conversion formula: For example, if H202 1V% is insufficient, 10004
X0.01=lOQ of H, O, must be replenished. Therefore, H20, the pump is (10/6)X60=1
Figure 11 shows the KMnO, pump turn-on time, and H, O, concentrations under condition ①, which must operate for 00 seconds.
H, 0, pump O] is a relationship diagram with time.

Therefore, H. 0. The pump time will be:

y= IOOXZx +,oo2 63×Z -10oz-200 1■6...Formula■ c Summary of formulas■, ■, ■] By the above formula, KM under each condition F of ■, ■, ■
Knowing the H, 0, replenishment pump time from the n04 pump time becomes a town ability.

The table below summarizes the H2O2 bomb on time conversion formula.

In the above table, A is the concentration of KMnO4 (N), and B is the concentration of KMnO4 (N).
is KMnO, pump flow rate (ml/min), C is sampling pump flow rate, D is H. O. Supply pump flow f4
(ml/min, assuming tank capacity 81000Q),
E is the maximum value of KMnO and pump on time, G is the formula for determining H202 concentration W from KMnO and pump on time X, and H is H. This is a formula for calculating the 02 bomb on time Y from KMnO, pump on time X, H20, and concentration setting value Z.

FIGS. 12(A) and 12(B) are flowcharts showing the operations of the H, O, and controllers.

This device is used by storing various data necessary for calculation in advance in the memory built into the controller 1/roller 17, and when storing data, turn on the data switch and input the data. When the data input is completed, the data switch 7 is turned from on to off. The data switch is left off unless the data is rewritten. Does this program start when you turn on the power switch? H202 concentration measurement and control operations will not be performed unless the switch is turned on. Hereinafter, the program will be specifically explained according to FIGS. 12(A) and 12(B).

(a) “Initialize” It is initialized when the power is turned on.

(Mouth) "Data: , set?" After initialization is completed, it is determined whether the data switch is on or not.

(c) "HzOz% set?" If the judgment result of step (mouth) is yes Y, ■1■02
It is determined whether the target value setting operation for concentration (%) has been performed.

(2) ``% Data Input'' If the determination result in step (c) above is YES, input the target value specified by the setting operation.

(e) "Alarm upper limit value?" If step (2) is completed or step (c)
If the determination result is NO N, it is determined whether or not an action to set the upper limit value of the column has been performed.

(v) "Input alarm upper limit value" If the judgment result of step (e) is YES, enter the alarm upper limit value specified by the setting operation.

(g) "Alarm lower limit value?" If the determination result in step (e) is NO, or if the operation in step (g) is completed, it is determined whether the alarm lower limit value setting operation has been performed.

(H) "Alarm lower limit value input" When Stesog(g) is completed, input the alarm lower limit value according to the setting operation.

(ri) "End?" Step 7 If the judgment result in step (g) is N, or if step (h) is completed, it is determined whether the data center is completed. If the judgment result is NO/KUN, return to step (c).

(nu) 1 start? ” If the judgment result of Step 7 is NO, or if the judgment result of Step (RI) is Yes, Y, then check whether the start switch is turned on or not until a judgment result of YES Y is obtained. Repeat.

(l) "1 rain open" If the judgment result in step (n) is yes, open the drain 18.

(w) "Sampling pump on for 600 seconds" Next, the sampling pump 9 is turned on for 600 seconds to replace the sampling aqueous solution. This is done to completely remove any residual liquid in the tube.

(W) [Drain closed Next, drain l8 is closed.

(Power) "Starrer On" Next, the stirring bar (stirrer) 14 is rotated.

(Yo) “Funnel washing for 30 seconds” Next, the water washing pump 3 is turned on for 30 seconds.

(Evening) "Open the drain for 30 seconds" Next, open the drain 18 and drain the liquid in the reaction tank (funnel) 1.

(v) [Number of times count +1 Next, the built-in counter that counts the number of times of washing with water (including cases in which there is no hardware-specific counter and functions as a software-like counting function) is incremented by 1.

(n) "Number of times count value - 3" Next, it is determined whether or not the count value of the counter has reached 3. If the judgment result is NO, step (Y)
Return to

Note that steps (l) to (n) are for removing residual liquid.

(T) rH. So, pump 11 is turned on for 108 seconds" If the judgment result in step (So) is yes (when three washings are completed), then H, So, the pump 11 is turned on for 108 seconds to supply the diluent.

(Un) "Sampling pump on for 60 seconds" Next, the sampling pump 9 is turned on for 60 seconds to supply the main solution containing hydrogen peroxide from the tank 6 into the reaction tank (funnel) 1.

(4) Turn on the KMnO pump Next, turn on the KMn04 pump 5 to supply a fixed amount of KMnO to the reaction tank 1 per unit time.

(Ra) [20 seconds have passed? Next, it is determined whether 20 seconds have passed after the end of step (n) until a determination result of YES is obtained.

(MU)FORP=800mV? If the determination result of the J step (A) is YES Y, it is continued to determine whether the ORP value by the ORP electrode 13 has reached 800 mV until a YES Y determination result is obtained.

(c) rKMnO, pump off” When the judgment result of step (m) is YES Y, KM
nO. Turn off pump 5.

(2) Set time until r800mV Next, set the time-lapse result X of the time required for the ORP value to reach 800mV.

(E) From UX I{,O! Concentration Calculation Next, H,0,concentration is calculated using an arithmetic formula for calculating H,0,concentration from time X (this has already been explained in detail).

(H) “Concentration display” Next, the concentration calculated in step (e) is displayed.

(Y) “Are you above the upper limit?” Next, it is determined whether the concentration is greater than or equal to the upper limit value.

(M) "Is it below the lower limit?" If the determination result in step (Y) is NO, it is determined whether the concentration is below the lower limit.

(k) "Alarm output on" If the judgment result in step (Y) or (M) is yes, turn on the alarm output. This allows the worker to know that an abnormality has occurred.

(W) "Alarm stop?" Next, it is determined whether or not a preset alarm action has been performed until a YES determination result is obtained.

(J) "Turn off alarm output" If the determination result in step (7) is yes, turn off the alarm output. The alarm will then stop.

(Engineer) "H from X, 0, pump time ym ratio" step (
If the judgment result of
2 Calculate and set the time to operate the H202 pump from the target set value Z of the 202 concentration.

(Te)’HzOtbonpuon” HtO! Turn on pump 8.

(a) ry seconds have elapsed” Determine whether Y seconds have elapsed since the H, O, and pumps 8 were turned on.

(S) 'H*Ox Bomb Off' When the judgment result of step (a) is yes Y
xO! Turn off Ponzo 8. As a result, the missing H
．． O, this means that the replenishment of pure liquid has been completed.

The subsequent steps (k) to (mi) are for removing chemical reaction scale (dross).

(K) “Drain on for 30 seconds” Next, the drain 18 is turned on for 30 seconds to discharge the water.

(Yu) 1 funnel wash for 30 seconds” Next, wash with water for 30 seconds.

(Me) [Number of times count +1] Count up the number of washes by 1.

(Mi) “Number of times count -3?” It is determined whether the number of times of washing has reached three times.

If the determination result is NO N, the process returns to step (K).

(S)rl800 seconds have passed? ” If the determination result in step (mi) is yes, Y, it is determined whether 1800 seconds have elapsed since step (ru) of opening the drain was started. If the determination result is YES Y, the process returns to step (R).

(M) "Stop?" If the determination result in step (C) is NO, it is determined whether an operation to turn off the start switch has been performed. If the judgment result is NO, the process returns to step (C), and if the judgment result is YES, the process returns to step (C).

[Effect of the invention 1 As is clear from the above description, according to the present invention, potassium permanganate is titrated into an aqueous solution to be measured in a fixed amount per unit time, and hydrogen peroxide is titrated from the time required to reach the end point. Since the concentration of potassium permanganate is measured, the measurement accuracy is determined by the amount of potassium permanganate supplied per unit time, and the measurement accuracy can be easily increased by reducing the amount of potassium permanganate supplied.

Furthermore, in this method, the redox reaction between hydrogen peroxide and potassium permanganate is not affected by the concentration, and furthermore, because the dispersibility in the reaction tank is very good, it is hardly affected by shared substances.

Therefore, it can contribute to improving measurement accuracy.

[Brief explanation of drawings]

The drawings are for explaining one embodiment of the present invention.
The figure is an overall configuration diagram, Figures 2 (A') and (j3) are perspective views showing different examples of stirring rods, Figure 3 is a plan view of the reaction tank,
Figure 4 is a longitudinal cross-sectional view of the reaction tank, Figure 5 is a diagram of the relationship between potassium permanganate titration and ORP value, and Figures 6 to 8 are the potassium permanganate bonzo operating time under different conditions. Relationship diagrams of hydrogen peroxide concentration, Figures 9 to 11 are relationship diagrams between the operating time and hydrogen peroxide concentration of the potassium permanganate supply pump and the hydrogen peroxide replenishment pump operating time under different conditions. , FIGS. 12(A) and 12(B) are flowcharts showing the operation.・Reaction tank ・Potassium permanganate pump ・Hydrogen peroxide supply pump ・Sampling pump ・Hydrogen peroxide controller (A) (B) 2 Figure 13 3 Figure H. 0, Concentration (V%)-H. 0,+: Time (seconds) -1 ↑! = D1 H,02 Pump time (J!P) - H,Q Cobb/Pump time (sec) -

Claims (1)

[Claims] (1) A certain amount of potassium permanganate is added per unit time to an aqueous solution containing hydrogen peroxide to cause a redox reaction, and the change in the ORP value detected by an ORP electrode immersed in the aqueous solution is determined based on the redox reaction. A method for measuring hydrogen peroxide concentration that detects the end point of the reaction and measures the concentration of hydrogen peroxide from the time required from the start of addition of potassium permanganate to the end point of the reaction. (2) a reaction tank; a test aqueous solution supplying means for supplying a test aqueous solution containing hydrogen peroxide to the reaction tank; and potassium permanganate supplying a constant amount of potassium permanganate per unit time to the reaction tank. A supply means, an ORP electrode immersed in a solution in a reaction tank, and a reaction end point is detected from a change in the ORP value detected by the ORP electrode, and the reaction end point is detected from the start of supply by the above-mentioned potassium permanganate supply means to be measured. A measuring device for hydrogen peroxide concentration, comprising: arithmetic means for calculating the concentration of hydrogen peroxide by measuring the time required to reach the hydrogen peroxide concentration, and calculating the concentration of hydrogen peroxide by multiplying the time by a predetermined coefficient.