A method for measuring the density of a liquid using a solution of optical rotation

Abstract

The application discloses a method for measuring liquid density by using optical active solution, which comprises a laser, a polarizer, a liquid to be measured, an optical active solution, a transparent water tank, an electronic balance, an analyzer and a light screen. γ The optical active solution is filled in the transparent water tank with a length of l, and the mass of the optical active solution is γ, the mass of the solute is γ1, and the density is ρ X A certain mass (X) of the liquid to be measured is added, and after being uniformly stirred, the optical activity α of the mixed solution is measured by rotating the analyzer and the light screen; the relationship between X and α is obtained, that is, the data are linearly fitted by using a graphing method, and the density ρ X of the liquid to be measured is calculated by the slope of the straight line. The application is a method for measuring liquid density, and has clear physical principle, simple measurement process, high measurement accuracy and high repeatability.

Description

Technical Field

[0001] This invention relates to a method for measuring the density of a liquid, specifically a method for measuring the density of a liquid using an optically active solution. Background Technology

[0002] When plane-polarized light passes through a solution of certain crystals or substances, the plane of vibration rotates about the axis of light propagation; this phenomenon is called optical rotation. Crystals or solutions exhibiting optical rotation are called optically active substances, and the angle of deflection is called optical rotation. The magnitude of optical rotation is related to the thickness and physical properties of the substance. By studying the optical rotation properties of substances, we can identify their types and analyze parameters such as concentration, content, and purity.

[0003] Density is also one of the important physical parameters of liquids. By measuring density, substances with similar but different chemical compositions can be distinguished, and the purity of a liquid can be determined. In industrial production inspection, density is one of the quality control indicators for many liquid products. Existing methods for measuring the density of transparent solutions mainly include the specific gravity method, the density bottle method, and the glass float meter. However, methods for measuring the density of other liquids using optically active solutions have not been reported.

[0004] This invention involves mixing the solution to be tested with a known optically active solution, measuring the optical rotation of the mixed solution, establishing the relationship between the mass of the liquid to be tested and the optical rotation of the mixed solution, and then calculating the density of the solution to be tested. Summary of the Invention

[0005] The purpose of this invention is to provide a method for measuring the density of a liquid by measuring the optical rotation of a mixed solution (a mixture of X mass of the liquid to be tested and a known optically active solution) to calculate the density of the liquid to be tested.

[0006] Therefore, the present invention adopts the following technical solution: including a laser, a polarizer, a liquid to be tested, an optically active solution, a transparent water tank, an electronic balance, an analyzer, and a screen; during measurement, the transparent water tank contains an optically active solution, the mass of which is known to be Y, the mass of the solute to be Y1, and the density to be ρ. Y A certain mass (X) of the liquid to be tested is added, and after stirring evenly, the optical rotation α of the mixed solution is measured by rotating the analyzer and observing the brightness of the light spot on the screen; the relationship between X and α is then obtained, i.e. The density ρ of the liquid under test is calculated from the slope of the straight line by using a graphical method and linear fitting of the data. X .

[0007] The measurement principle is as follows:

[0008] From the given conditions, we know that the volume of the optically active solution is... Assume the density of the liquid to be measured is ρ XThe mass added is X. Ignoring volume changes, the total volume of the two liquids after mixing is...

[0009]

[0010] At this point, the concentration of the mixed optically active solution is

[0011]

[0012] The formula for the optical rotation α of an optically active solution is the product of specific rotation, length, and concentration.

[0013]

[0014] Combining (1), (2), and (3), we can obtain the mathematical expression for the concentration of the liquid to be measured.

[0015]

[0016] The specific measurement steps are as follows:

[0017] Step 1: Adjust the instrument. The laser passes through the polarizer, the transparent water tank, and the analyzer in sequence to form a light spot on the screen. Rotate the analyzer to change the brightness of the light spot. When the transparent water tank is empty and the light spot is the darkest, the analyzer scale reading is θ0.

[0018] Step 2: Configure the concentration as follows A solution with optical rotation, mass Y, and volume V. Y Then density Solute mass is

[0019] Step 3: Pour all the optically active solution into a transparent water trough. Tare the electronic balance reading to zero, and observe the brightening of the light spot. Rotate the analyzer to the extinction state, making the light spot as dark as possible. Record the analyzer reading at this point as θ′0. The optical rotation is then α0 = θ′0 - θ0. Calculate the specific rotation of the optically active solution. Where l is the length of the transparent water tank.

[0020] Step 4: Add a certain mass of the test liquid to the optically active solution. The electronic balance reading is X1. After stirring evenly, the light spot becomes brighter. Rotate the analyzer to the extinction state to make the light spot the darkest. Record the analyzer reading at this time as θ1. Then the optical rotation is α1 = θ1 - θ0.

[0021] Step 5: Repeat step 4 to obtain the electronic balance reading as X2. Record the analyzer reading as θ2 when the light is extinct. Then the optical rotation is α2 = θ2 - θ0.

[0022] Step 6: Repeat steps 4 and 5 to obtain the relationship between X and α, i.e.

[0023] Step 7: Use a graphical method to... With x as the ordinate and x as the abscissa, the slope is obtained by fitting the experimental data. Calculate the density ρ of the liquid to be tested. X .

[0024] More preferably, the laser emits a 632.8nm laser, making the changes in the brightness of the light spot clear.

[0025] More preferably, in the third step above, the specific rotation... The measurement was repeated multiple times to ensure that the measurement value at a wavelength of 632.8nm and a temperature of 20℃ had the smallest error.

[0026] More preferably, in the fourth and fifth steps above, after adding a certain mass of the test liquid to the optically active solution, it must be stirred evenly and the optical rotation α must be measured after the mixed solution has stabilized.

[0027] More preferably, throughout the entire testing process, including adding the liquid to be tested, stirring the mixed solution, and rotating the analyzer, the positions of the optical path and the transparent water tank must remain fixed.

[0028] More preferably, the above-mentioned electronic balance directly weighs the mass of the added liquid to be tested, which improves the measurement accuracy.

[0029] More preferably, the analyzer is equipped with a vernier caliper with an accuracy of up to 5', which makes the angle measurement during extinction more accurate.

[0030] More preferably, the aforementioned screen can be replaced with a high-sensitivity photodetector, which also makes the angle measurement during extinction more accurate.

[0031] The beneficial effects of this invention are: by adding a known optically active solution to a transparent water tank and measuring its optical rotation, the specific optical rotation of the known optically active solution at that temperature T and that laser wavelength λ can be obtained. (One of the physical parameters of optically active solutions); subsequently, by simply adding different masses of the test solution multiple times and measuring the optical rotation of the mixed solution, the density of the test liquid can be calculated. This invention features a simple instrument setup, a straightforward measurement method, a clear principle, obvious phenomena, and accurate measurements. It can be promoted as a method for measuring liquid density, expanding the application range of optically active solutions and is also suitable for use in experimental classroom teaching. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the measurement process of the present invention;

[0033] Figure 2The graph shows experimental data for a test solution of water (density 1.0 g / mL);

[0034] Figure 3 The graph shows the experimental data for a test solution of saline (density 1.161 g / mL);

[0035] In the diagram: 1. Laser, 2. Polarizer, 3. Liquid to be tested, 4. Optical rotation solution, 5. Transparent water tank, 6. Electronic balance, 7. Analyzer, 8. Screen. Detailed Implementation

[0036] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0037] The measurement schematic diagram provided by this invention is as follows: Figure 1 As shown. A sucrose solution was selected as the optically active solution, and water or a saline solution was used as the test liquid for the experiment.

[0038] Example 1 (using water as the test liquid)

[0039] The operation steps are as follows:

[0040] 1. First step: Adjust the instrument, turn on laser 1, and emit a 632.8nm red laser as the incident light for testing. The laser light passes through polarizer 2, transparent water tank 5, and analyzer 7 in sequence, forming a light spot on screen 8. When there is no liquid in the transparent water tank, rotate the analyzer to make the light spot the darkest. At this time, the analyzer scale reading is θ0 = 285°40′.

[0041] Step 2: Configure the concentration as follows A solution with optical rotation has a mass of 110.5 g and a volume of V. Y =100ml, then density The bulk quality is

[0042] Step 3: Pour all of the sucrose solution 4 into the transparent water trough (the length of the solution l = 1.1456 dm). The electronic balance 6 is tare-dimmed and reads zero. The light spot becomes brighter. Rotate the analyzer to the extinction state to make the light spot the darkest. Record the analyzer reading at this point as θ′0 = 303°20′. Then, the optical rotation α0 = θ′0 - θ0 = 17°40′. Calculate its specific rotation.

[0043] Step 4: Add 25g of water to the sucrose solution. The electronic balance reading is 25.0g (X1 = 25g). A mixed solution of sucrose and water is obtained, which is equivalent to a diluted sucrose solution. After stirring evenly, the light spot becomes brighter. Rotate the analyzer to the extinction state to make the light spot the darkest. Record the analyzer reading at this time as θ1 = 299°50′. Then the optical rotation α1 = θ1 - θ0 = 14°10′.

[0044] Step 5: Repeat step 4 to obtain an electronic balance reading of 50g (X2 = 50g). When the extinction state is recorded, the analyzer reading is θ2 = 297°35′. Then the optical rotation α2 = θ2 - θ0 = 11°55′.

[0045] Step 6: Add 25g of water twice more, i.e., X3 = 75g and X4 = 100g. Calculate the analyzer readings θ3 and θ4 at extinction, and the optical rotations α3 and α4, to obtain the relationship between X and α. The measurement data are shown in Table 1.

[0046] Step 7: As Figure 2 As shown, a graphical method is used to... With x as the ordinate and x as the abscissa, the slope is obtained by fitting the experimental data. The measured density of water is 1.0177 g / ml, which is only 1.8% less than the actual density of water (1.0 g / ml).

[0047] Table 1. Measurement data using water as the test solution.

[0048]

[0049] Example 2 (using a saline solution as the test liquid)

[0050] The operation steps are as follows:

[0051] Step 1: Adjust the instrument, turn on laser 1, and emit a 632.8nm red laser as the incident light for testing. The laser light passes through polarizer 2, transparent water tank 5, and analyzer 7 in sequence, forming a light spot on screen 8. When there is no liquid in the transparent water tank, rotate the analyzer to make the light spot the darkest. At this time, the analyzer scale reading is θ0 = 285°40′.

[0052] Step 2: Configure the concentration as follows A solution with optical rotation has a mass of 110.5 g and a volume of V. Y =100ml, then density Solute mass is

[0053] Step 3: Pour all of the sucrose solution 4 into the transparent water trough (the length of the solution l = 1.1456 dm). The electronic balance 6 is tare-dimmed and reads zero. The light spot becomes brighter. Rotate the analyzer to the extinction state to make the light spot the darkest. Record the analyzer reading at this point as θ′0 = 303°20′. Then, the optical rotation α0 = θ′0 - θ0 = 17°40′. Calculate its specific rotation.

[0054] Step 4: Add 25g of salt solution to the sucrose solution. The electronic balance reading is 25.0g (X1 = 25g). A mixed solution of sucrose and salt solution is obtained. After stirring evenly, the light spot becomes brighter. Rotate the analyzer to the extinction state to make the light spot the darkest. Record the analyzer reading at this time as θ1 = 300°15′. Then the optical rotation α1 = θ1 - θ0 = 14°35′.

[0055] Step 5: Repeat step 4 to obtain an electronic balance reading of 50.0g (X2 = 50g). When recording the extinction state, the analyzer reading is θ2 = 298°5′. Therefore, the optical rotation α2 = θ2 - θ0 = 12°25′.

[0056] Step 6: Add 25g of salt solution twice more, i.e., X3 = 75g and X4 = 100g. Calculate the analyzer readings θ3 and θ4 at extinction, and the optical rotations α3 and α4, to obtain the relationship between X and α. The measurement data are shown in Table 2.

[0057] Step 7: As Figure 3 As shown, a graphical method is used to... With x as the ordinate and x as the abscissa, the slope is obtained by fitting the experimental data. The measured density of the salt solution was 1.1867 g / ml. The density of the salt solution in the experiment was 1.161 g / ml, so the measurement error was only 2.2%.

[0058] Table 2. Measurement data using saline solution as the test solution.

[0059]

[0060] It is evident that the method for measuring liquid density using optically active solutions provided by this invention has small measurement errors and is effective.

[0061] The above descriptions are merely two embodiments of the present invention and do not limit the scope of the patent. Therefore, any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A method for measuring the density of a liquid using a solution of optical rotation, characterized in that, The application relates to a polarimeter, which comprises a laser, a polarizer, a liquid to be measured, a solution with optical rotation, a transparent water tank, an electronic balance, an analyzer and a light screen; when measuring, the solution with optical rotation is filled in the transparent water tank, the mass of the solution with optical rotation is known as gamma, the mass of the solute is gamma1, and the density is rho Y ; the liquid to be measured with the mass of X is added, the mixed solution is stirred uniformly, the light and shade of the light spot on the rotating analyzer and the light screen are measured, and the optical rotation degree alpha of the mixed solution is obtained; the liquid to be measured is continuously added, the optical rotation degree of the mixed solution is measured, and the relationship between the optical rotation degree and the mass of the liquid to be measured is obtained; the process is repeated for several times. The relationship between X and a is obtained, that is Finally, the plotting method is used, the data are linearly fitted, and the density p of the liquid to be measured is calculated from the slope of the straight line X The specific measurement steps are as follows: First step: adjust the instrument, laser through the polarizer, transparent tank, analyzer, on the screen to form a light spot, rotating the analyzer, light spot brightness changes, when the transparent tank is empty, and the light spot is the darkest, the analyzer scale reading is θ0, at this time the optical rotation is 0, Second step: configuration of the starting optically active solution with concentration C Y1 , mass γ, and volume V Y . Then the density p Y = γ / V Y , the solute mass Y1= C Y1 V Y , Third step: pour all the optical rotation solution into the transparent water tank, the electronic balance reading is peeled off, showing zero, the light spot is found to be brighter, rotate the analyzer to the extinction state, make the light spot darkest, record the analyzer reading at this time as θ'0, then the optical rotation is α0= θ'0- θ0, calculate the specific optical rotation of the optical rotation solution where l is the length of the transparent water tank, Fourth step: in the optically active solution, add a certain mass of the liquid to be measured, the electronic balance reading is X1, get the mixed solution, after stirring, the light spot becomes brighter, rotate the analyzer to the extinction state, the light spot is the darkest, record the analyzer reading at this time θ1, the optical rotation is α1= θ1- θ0, Fifth step: repeat the fourth step process, get the electronic balance reading X2, record the analyzer reading θ2 in the extinction state, the optical rotation is α2= θ2- θ0, Step 6: Repeat the process of steps 4 and 5 to obtain X i The relationship between a i The relationship between a Step 7: Using the plotting method, take as the ordinate and X as the abscissa, fit the experimental data to obtain the slope of the line X . Calculate the density of the liquid to be measured ρ X .

2. The method of claim 1, wherein the polarized light solution is a solution of potassium thiocyanate. The laser emits 632.8nm laser, so that the light spot bright and dark change phenomenon is clear.

3. The method of claim 1, wherein the polarized light solution is a solution of potassium thiocyanate. In the third step, the specific optical rotation was measured several times to ensure the minimum error in the measured value at a wavelength of 632.8 nm and 20°C. The measurement of the specific optical rotation was repeated several times to ensure the minimum error in the measured value at a wavelength of 632.8 nm and 20°C.

4. The method of claim 1, wherein the polarized light solution is a solution of potassium thiocyanate. In steps four and five, after adding a certain mass of the test liquid to the optically active solution, it is essential to stir thoroughly and wait for the mixed solution to stabilize before measuring the optical rotation α. i Measurement.

5. The method of claim 1, wherein the polarized light solution is a solution of potassium thiocyanate. During the whole test process, including adding the liquid to be measured, stirring the mixed solution, rotating the analyzer, the position of the light path and the transparent tank is fixed.

6. The method of claim 1, wherein the polarized light solution is a solution of potassium thiocyanate. The analyzer is provided with a vernier scale, the accuracy can reach 5', the angle measurement in the extinction state is more accurate.

7. The method of claim 1, wherein the polarized light solution is a solution of potassium thiocyanate. The screen can be replaced by a high sensitivity photoelectric detector, which also makes the angle measurement in the extinction state more accurate.

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