An experimental device and experimental method for measuring concentration of mixed solution

Abstract

The application belongs to the technical field of mixed solution concentration measurement, and discloses an experimental device for measuring the concentration of a mixed solution, comprising an optical bench, wherein a base plate is slidably connected to the top of the optical bench, and a polarizer and an analyzer are slidably connected to the side of the optical bench close to the base plate, and an experimental method for measuring the concentration of a mixed solution is disclosed, comprising the following steps: S1: adding the solution to be detected after configuration into the inside of a container, and placing the container between the two Helmholtz coils on the top of the base plate. The application adopts the turning-back method for the first time. Since the rotation direction of natural optical rotation is related to the propagation direction of light, but the rotation direction of magnetic optical rotation is irrelevant to the propagation direction of light, and only depends on the direction of the applied magnetic field, in theory, the influence of the solution with natural optical rotation is avoided, the natural optical effect caused by the geomagnetic field, external magnetic field and the like is eliminated, and the deflection angle of the magnetic optical rotation is doubled, thereby ensuring the accuracy of the obtained value.

Description

An experimental apparatus and method for measuring the concentration of a mixed solution. Technical Field

[0001] This invention belongs to the field of transparent liquid measurement technology, specifically relating to an experimental apparatus and method for measuring the concentration of mixed solutions. Background Technology

[0002] The measurement of solution concentration has wide applications in industries such as papermaking, chemical engineering, sugar refining, dairy products, pharmaceuticals, and beverages. The concentration of transparent liquids is widely used in both daily life and scientific research; therefore, its measurement is an important part of physics. Research in this field generally uses methods such as indirect density measurement, capacitance sensor methods, and float methods. Indirect density measurement requires self-made equipment and has a long measurement cycle, although the design of the apparatus is relatively simple. Capacitance sensor methods can improve accuracy through data fusion. The float method uses the specific gravity of the liquid to convert it to solution concentration, but the experimental setup is relatively large. Each of these methods has its own drawbacks, and research on the concentration of mixed solutions is lacking. However, most solutions in daily life are mixed solutions; therefore, it is crucial to invent new methods applicable to the measurement of the concentration of various transparent liquids. Summary of the Invention

[0003] The purpose of this invention is to provide an experimental apparatus and method for measuring the concentration of a mixed solution, so as to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the present invention provides the following technical solution: an experimental apparatus for measuring the concentration of a mixed solution, comprising an optical bench, a substrate slidably connected to the top of the optical bench, a polarizer and an analyzer slidably connected to one side of the top of the optical bench near the substrate, and two rotatable mirrors slidably connected to the other side; two Helmholtz coils symmetrically placed on the top of the substrate, and a container placed on the top of the substrate near the side between the two coils; a laser slidably connected to one side of the top of the optical bench between the polarizer and the top of the optical bench, and a sensor slidably connected to one side of the top of the optical bench between the analyzer and the top of the optical bench.

[0005] Preferably, the experimental apparatus for measuring the concentration of the mixed solution further includes a power supply electrically connected to a Helmholtz coil.

[0006] Preferably, the spacing between the two Helmholtz coils is equal to the radius of the Helmholtz coil.

[0007] Preferably, the container is a cuboid container and is made of a light-transmitting material.

[0008] Preferably, the sensor includes a photoresistor and is electrically connected to an ohmmeter.

[0009] An experimental method for measuring the concentration of a mixed solution includes the following steps:

[0010] S1: Add the prepared solution to be tested into the container and place the container between the two Helmholtz coils on the top of the substrate;

[0011] S2: Power the Helmholtz coil through the power supply, and use a voltmeter to detect whether the power supply has successfully provided voltage to the Helmholtz coil;

[0012] S3: Pull the polarizer, reflector, analyzer, sensor and laser to adjust the position and angle of the polarizer, reflector, analyzer, sensor and laser;

[0013] S4: Turn on the laser switch to let the light source shine on the photoresistor in the sensor and record the value of the ohmmeter in the sensor;

[0014] S5: Repeat the above steps with other solutions of different concentrations.

[0015] S6: Repeat the above operation with other lasers of different wavelengths to calculate the optical rotation angle at different concentrations;

[0016] S7: Measure the concentration of the mixed solution and repeat the above operation.

[0017] Preferably, the photoresistor is a 5528 type photoresistor.

[0018] Preferably, the step of turning on the laser switch to illuminate the photoresistor in the sensor and recording the value of the ohmmeter in the sensor includes the following steps:

[0019] S41: Before the experiment, adjust the optical path of the laser so that the incident light rays are symmetrical with respect to the central axis of the Helmholtz coil.

[0020] Preferably, the step of adding the prepared solution to be tested into the container and placing the container between the two Helmholtz coils on top of the substrate includes the following steps:

[0021] S11: Move the device to a dark room and maintain a constant temperature.

[0022] Preferably, the concentration of the solution is 3g / 100ml-29g / 100ml.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] (1) This invention is the first to use the folding method. Since the rotation direction of natural optical rotation is related to the direction of light propagation, but the rotation direction of magneto-optical rotation is not related to the direction of light propagation, but only depends on the direction of the external magnetic field. Theoretically, it avoids the influence of the solution's natural optical rotation, eliminates the natural optical rotation effect caused by the geomagnetic field, external magnetic field, etc., and doubles the deflection angle of magneto-optical rotation to ensure the accuracy of the obtained value.

[0025] (2) The present invention designs an optical path diagram and combines the Faraday effect and the magneto-optical rotation effect to use the optical intensity probe method, which can realize the measurement of the concentration of each of the various solutions after mixing. The numerical value can be obtained quickly through programming. Furthermore, the components of the mixed solution can be solutes that do not affect each other and have the same optical rotation direction. The optical rotation angle obtained by this method has little deviation and the results are relatively good. Attached Figure Description

[0026] Figure 1 is a schematic diagram of the structure of the present invention;

[0027] Figure 2 is a schematic diagram showing the relationship between the solution concentration and optical rotation angle of the present invention;

[0028] Figure 3 is a comparison of the theoretical and experimental values ​​of the mixed solutions of different concentrations of the present invention;

[0029] In the diagram: 1. Polarizer; 2. Helmholtz coil; 3. Container; 4. Mirror; 5. Sensor; 6. Laser; 7. Optical bench; 8. Power supply; 9. Substrate; 10. Analyzer. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Please refer to Figures 1-3. The present invention provides the following technical solution:

[0032] An experimental apparatus for measuring the concentration of a mixed solution includes an optical bench 7, a substrate 9 slidably connected to the top of the optical bench 7, a polarizer 1 and an analyzer 10 slidably connected to one side of the top of the optical bench 7 near the substrate 9, and two self-rotating mirrors 4 slidably connected to the other side.

[0033] Two Helmholtz coils 2 are symmetrically placed on the top of the substrate 9, and a container 3 is placed on the top of the substrate 9 near the side between the two 2s;

[0034] A laser 6 is slidably connected to one side between the top of the optical bench 7 and the polarizer 1, and a sensor 5 is slidably connected to one side between the top of the optical bench 7 and the analyzer 10.

[0035] The device also includes a power supply 8, which is electrically connected to the Helmholtz coil 2;

[0036] The distance between the two Helmholtz coils 2 is equal to the radius of the Helmholtz coil 2;

[0037] Container 3 is a rectangular container and is made of a light-transmitting material;

[0038] Sensor 5 includes a photoresistor and is electrically connected to an ohmmeter.

[0039] An experimental method for measuring the concentration of a mixed solution includes the following steps:

[0040] A1: Move the apparatus to a darkroom with constant temperature for the procedure;

[0041] A2: Add the prepared solution with a concentration of 3g / 100ml-29g / 100ml to be tested into the inside of container 3, and place container 3 between the two Helmholtz coils 2 on the top of substrate 9;

[0042] A3: Power supply 8 is used to supply power to Helmholtz coil 2. A voltmeter is used to check whether power supply 8 has successfully supplied voltage to Helmholtz coil 2.

[0043] A4: Pull the polarizer 1, reflector 4, sensor 5, laser 6, and analyzer 10 to adjust the position and angle of the polarizer 1, reflector 4, analyzer 10, sensor 5, and laser 6.

[0044] A5: Turn on the switch of laser 6 so that the light source shines on the photoresistor in sensor 5. The photoresistor is a 5528 type photoresistor. Record the value of the ohmmeter in sensor 5.

[0045] A6: Repeat the above steps with other solutions of different concentrations.

[0046] A7: Repeat the above operation with other lasers of different wavelengths to calculate the optical rotation angle at different concentrations;

[0047] A8: Before the experiment, adjust the optical path of laser 6 so that the incident light rays are symmetrical with respect to the central axis of Helmholtz coil 6.

[0048] A9: Measure the concentration of the mixed solution and repeat the above operation.

[0049] Furthermore, in this invention, when linearly polarized light passes through certain crystals and some liquids and gases, its vibration plane gradually rotates as the distance the light travels in the substance increases. This phenomenon is called optical rotation.

[0050] For optically active solutions, which exhibit both spontaneous optical rotation and magneto-optical rotation, the angle φ of the vibrational surface rotation is directly proportional to the distance d transmitted through the solution and the concentration C of the solution, i.e.:

[0051] φ=[α]Cd

[0052] The proportionality constant [α] is called the specific optical rotation of the solution. Note: Many organic solutions are optically active.

[0053] If a magnetic field is applied to a medium in a direction parallel to the light ray, many substances that are not normally optically active will acquire this property. This phenomenon is called the Faraday effect or magneto-optical rotation. The angle of rotation φ is proportional to the magnetic field strength B, and the direction of rotation depends only on the direction of the magnetic field and is independent of the direction of light propagation. For a Helmholtz coil with a magnetic field applied, if the currents in the two coils are in the same direction and equal in magnitude, and the distance between the two coils is equal to the radius of the coils, a uniform magnetic field is generated.

[0054] Light intensity after polarizer: I = I0cos 2 (a)(I0 light intensity after passing through the polarizer, where a is the angle between the polarizer and the analyzer)

[0055] Magnetic field strength: B = B0sin(wt)

[0056] Light intensity after passing through the medium:

[0057] The experiment was conducted in a dark room, using the controlled variable method to fix the magnetic field, the distance through the solution, and the laboratory temperature. A 5528 photoresistor was used to measure the optical rotation angle when light passed through solutions of different concentrations. The conversion formula between light intensity and R was given when the ohmmeter reading was R:

[0058] ln(R) = -0.638ln(I) + 2.48

[0059] Finally, the optical rotation angle φ was obtained, and the fitted data yielded: φ = kc + b (c is the solution concentration, b is the angle fitted by the intensity change caused by partial reflection of light after passing through water, and k is the optical rotation).

[0060] Because optical rotation is additive—that is, the total optical rotation of a mixed solution is the sum of the individual optical rotations of its components—we can use this property to determine the concentration of each solute in a mixed solution (where the solutes do not react with each other). In this experiment, two mixed solutions (NaCl, KCl) with the same optical rotation direction are used. Since the solutions contain two different solutes, we need two different lasers for the experiment.

[0061] Red light passing through NaCl solution yields φ1 = k1c1 + b1;

[0062] Red light passing through a KCl solution yields φ2 = k2c2 + b2;

[0063] Green light passing through NaCl solution yields φ3 = k3c1 + b3;

[0064] Green light passing through a KCl solution yields φ4 = k4c² + b4;

[0065] In conclusion:

[0066] Red light passing through the mixed solution yields an optical rotation angle of φ1+φ2; green light passing through the mixed solution yields an optical rotation angle of φ3+φ4.

[0067] φ1+φ2=k1c1+b1+k2c2+b2;

[0068] φ3+φ4=k3c1+b3+k4c2+b4;

[0069] Solving the above equations yields c1 and c2.

[0070] Similarly, we can use light of n wavelengths to measure the concentration of solutes in n mixed solutions.

[0071] φ1=k1c1+b1+k2c2+b2+k3c3+b3+…+k n c n +b n ;

[0072] φ1=k n+1 c1+b n+1 +k n+2 c2+b n+2 +k n+3 c3+b n+3 +…+

[0073] k 2n c n +b 2n ;

[0074] ...

[0075] Solving the system of equations yields c1, c2, ..., cn.

[0076] Furthermore, in this invention, since the optical rotation angle is directly proportional to the magnetic field strength, meaning the optical rotation angle depends on the strength of the external power supply, a smaller magnetic field results in a smaller optical rotation angle, which can lead to greater experimental errors. Therefore, this experiment uses a relatively large voltage of 12V. Because the experimental results are affected by external temperature and light, attention should be paid to the ambient temperature and experimental location before the experiment.

[0077] The direction of spontaneous optical rotation is related to the direction of light propagation, while the direction of magneto-optical rotation is independent of the direction of light propagation and depends only on the direction of the applied magnetic field. Both belong to optical rotation effects. Magneto-optical rotation originates from the Zeeman effect, where plane-polarized light rotates its polarization plane when passing through a medium in a magnetic field along the direction of magnetic field lines. If the outgoing light is reflected back to the crystal, the linearly polarized light passing through the naturally optically rotating crystal will return to its original position after returning along the original path, while the linearly polarized light passing through the magneto-optical rotating crystal will continue to rotate, with its vibration plane making a larger angle with the original vibration plane. This experiment utilizes this property, employing a folding method with a plane mirror to design a folding optical path. The light passes through the solution twice. Since the magneto-optical rotation is in the same direction as the light propagation, this increases the deflection angle, and because the magnetic field is the same, it is equivalent to doubling the deflection angle. Simultaneously, because spontaneous optical rotation is related to the direction of propagation, the folding cancels each other out, eliminating the external effects that cause spontaneous optical rotation. This scheme enhances the magneto-optical rotation effect (deflection angle) while eliminating the spontaneous optical rotation effect caused by the material's own structure.

[0078] System error analysis

[0079] (1) In this experiment, since the magnetic field generated by the Helmholtz coil is not completely uniform, the symmetry of the incident rays in both directions relative to the Helmholtz coil can only ensure that the magnetic field at the corresponding positions is relatively equal.

[0080] (2) In this experiment, the voltage supplied to the Helmholtz coil by the instrument's constant power supply was too small to achieve the required magnetic field strength. Therefore, we used multiple dry cell batteries connected in series to power the Helmholtz coil. Since the voltage of the dry cell batteries decreased during the experiment, the generated magnetic field decreased, resulting in a certain error in the measurement results.

[0081] (3) In the experiment, the photoresistor will produce corresponding errors after being exposed to light for a long time. In the experiment, we can try to shorten the time when the light is exposed to the photoresistor to reduce such errors. Therefore, it is more reasonable to use the photoresistor as a sensor.

[0082] Experimental Precautions

[0083] (1) Before the experiment, the polarizer angle needs to be adjusted so that the resistance of the photoresistor reaches its maximum value.

[0084] (2) Before the experiment, the voltage across the coil must be measured to ensure that the voltage across the Helmholtz coil is equal.

[0085] (3) Before the experiment, the light path needs to be adjusted so that the incident light rays are symmetrical with respect to the central axis of the Helmholtz coil.

[0086] (4) Adjust the light during the experiment to ensure that the light is incident on the glass container.

[0087] (5) The experiment must be conducted in a dark room at a constant temperature.

[0088] Data processing and analysis

[0089] The intensity-based probe method, based on the magneto-optical rotation effect, offers a wider range of solution concentration measurements with more definitive experimental data. It can be used to measure the concentration of mixed liquids in everyday life. Below are the measurement results of the optical rotation angles of different concentrations of NaCl solution, KCl solution, and mixed solution (NaCl and KCl mixture) using red and green lasers at room temperature (25℃), with the results reflected by the photoresistor readings. Tables 1-3 show the experimental data for NaCl solution, KCl solution, and mixed solution, respectively.

[0090]

[0091] Table 1

[0092]

[0093] Table 2

[0094]

[0095] Table 3

[0096] In the experiment, the concentration of a single solution ranging from 3g / 100ml to 29g / 100ml was divided into 14 equal concentration intervals, and the experiment was conducted and the data was recorded for every 2g / 100ml.

[0097] Figure 2 shows the relationship between solution concentration and optical rotation angle. The measured optical rotation angles were linearized using Origin software. The resulting images are, in order: (A) NaCl under red laser irradiation, (B) NaCl under green laser irradiation, (C) KCl under red laser irradiation, and (D) KCl under green laser irradiation, the curves showing the change in solution concentration versus optical rotation angle. It can be seen that under the following four conditions, the fitted curves of optical rotation and concentration for each solution exhibit a linear relationship. The optical rotation of the solution increases significantly with increasing concentration, and the data points on the four graphs are basically consistent with the linearized lines, showing a positive proportional relationship. The correlation coefficient R is greater than 0.9 for all four graphs. From the degree of linearization, this innovative instrument can obtain accurate experimental data for solutions with different concentrations and different solutes.

[0098] The sources of error in the experimental results may include:

[0099] (1) There is an error in the estimation when preparing the solution.

[0100] (2) When the polarizer is adjusted to the maximum reading of the photoresistor, the accuracy of the angle is affected by the manual adjustment of the polarizer angle. However, the error is small and can be ignored.

[0101] By using empirical formulas to irradiate NaCl and KCl solutions separately with red and green light, we can calculate the theoretical value of the deflection angle of the mixed solution. As shown in Figure 3, the experimental measurement value of the mixed solution has a small error compared with the theoretical value, indicating that the experiment has high accuracy and strong reliability.

[0102]

[0103] Table 4

[0104] As shown in Table 4, the average value and standard deviation of the five sets of data obtained through multiple measurements are small, indicating that the data is highly accurate.

[0105] This experiment, based on the theory of magneto-optical rotation, designed a method for measuring the concentration of transparent liquids. It also innovated the measurement of mixed solution concentrations, refining the experimental scheme, apparatus design, and experimental verification. The group primarily employed the light intensity detection method, applying the optical rotation angle generated by the magnetic field provided by a Helmholtz coil to determine the liquid concentration. Analysis and comparison of the experimental results revealed that the maximum error for mixed solutions in the experimental data was 3.07%.

[0106] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An experimental apparatus for measuring the concentration of a mixed solution, characterized in that: The system includes an optical bench (7), on which a substrate (9) is slidably connected. A polarizer (1) and an analyzer (10) are slidably connected on one side of the top of the optical bench (7) near the substrate (9), and two self-rotating mirrors (4) are slidably connected on the other side. Two Helmholtz coils (2) are symmetrically placed on the top of the substrate (9), and a container (3) is placed on the top of the substrate (9) near the side between the two (2). A laser (6) is slidably connected on one side between the top of the optical bench (7) and the polarizer (1), and a sensor (5) is slidably connected on one side between the top of the optical bench (7) and the analyzer (10). The distance between the two Helmholtz coils (2) is equal to the radius of the Helmholtz coil (2).

2. The experimental apparatus for measuring the concentration of a mixed solution according to claim 1, characterized in that: It also includes a power supply (8), which is electrically connected to the Helmholtz coil (2).

3. The experimental apparatus for measuring the concentration of a mixed solution according to claim 1, characterized in that: The container (3) is a cuboid container and is made of a light-transmitting material.

4. The experimental apparatus for measuring the concentration of a mixed solution according to claim 1, characterized in that: The sensor (5) includes a photoresistor and is electrically connected to an ohmmeter.

5. An experimental method performed using the experimental apparatus for measuring the concentration of a mixed solution according to any one of claims 1-4, characterized in that: The process includes the following steps: S1: Add the prepared solution to be tested into the container (3), and place the container (3) between the two Helmholtz coils (2) on the top of the substrate (9); S2: Power the Helmholtz coils (2) through the power supply (8), and check whether the power supply (8) successfully provides voltage to the Helmholtz coils (2) through the voltmeter; S3: Pull the polarizer (1), mirror (4), sensor (5), analyzer (10) and laser (6) to adjust the position and angle of the polarizer (1), mirror (4), analyzer (10), sensor (5) and laser (6); S4: Turn on the laser (6) so that the light source shines on the photoresistor in the sensor (5) and record the value of the ohmmeter in the sensor (5); S5: Replace with other solutions of different concentrations and repeat the above operation; S6: Replace with other lasers (6) of different wavelengths and repeat the above operation to calculate the optical rotation angle at different concentrations; S7: Measure the concentration of the mixed solution and repeat the above operation.

6. The experimental method according to claim 5, characterized in that: The photoresistor is a 5528 type photoresistor.

7. The experimental method according to claim 5, characterized in that: The process of turning on the laser (6) to illuminate the photoresistor in the sensor (5) and recording the value of the ohmmeter in the sensor (5) includes the following steps: S41: Before the experiment, adjust the light path of the laser (6) so that the incident light rays are symmetrical with respect to the central axis of the Helmholtz coil (6).

8. The experimental method according to claim 5, characterized in that: The process of adding the prepared solution to be tested into the interior of the container (3) and placing the container (3) between the two Helmholtz coils (2) on the top of the substrate (9) includes the following steps: S11: moving the device to a dark room for constant temperature operation.

9. The experimental method according to claim 5, characterized in that: The concentration of the solution is 3g / 100ml-29g / 100ml.

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