A method for measuring the concentration of a transparent liquid

Abstract

The present invention discloses a method for measuring the concentration of a colorless and transparent liquid. The present invention measures the concentration of the colorless and transparent liquid by utilizing the change in the boiling point of the solution. After adopting the water replenishment operation, it can directly replenish the dissipated water, thereby reducing the measurement error and avoiding the phenomenon that when using Raoult's law to measure the concentration by boiling point, the solution concentration changes significantly due to the accelerated vaporization of the solvent caused by heating; the measuring device is simple, easy to operate, has high measuring accuracy, and low single measurement cost.

Description

Technical Field

[0001] The present invention relates to the technical field of liquid concentration measurement, and particularly relates to a method for measuring the concentration of transparent liquids. Background Art

[0002] The measurement of liquid concentration has always played a very important role in the chemical industry, materials science, food processing and other fields. The measurement of liquid concentration mainly uses the specific gravity method. With the development of technology and the needs of industrial production, some new methods have been developed recently. At present, many methods for measuring the concentration of solutions have been studied at home and abroad. Among them, the relatively mature and applied methods include the capacitance method, the optoelectronic method, the ultrasonic grating method, the grazing incidence method, electronic sensors, etc.

[0003] The existing technical solutions include the following several kinds: 1. Determining the concentration of a certain solution by titration method, also known as titrimetric analysis, which is a kind of chemical analysis method. A reagent solution with a known accurate concentration (called the standard solution) is added dropwise to the solution of the substance to be measured until the chemical reaction reaches the end point. Then, according to the concentration and volume of the reagent solution used, the content of the component to be measured can be obtained. This method is called titrimetric analysis (or volumetric analysis).

[0004] 2. Determining the concentration of a certain solution by spectrophotometry. In a spectrophotometer, when light of different wavelengths is continuously irradiated onto a sample solution with a certain concentration, absorption intensities corresponding to different wavelengths can be obtained. If the wavelength (λ) is used as the abscissa and the absorption intensity (A) is used as the ordinate, the absorption spectrum curve of the substance can be plotted. The method of using this curve for qualitative and quantitative analysis of substances is called spectrophotometry, also known as absorption spectrometry. The method of using an ultraviolet light source to measure colorless substances is called ultraviolet spectrophotometry; the method of using a visible light source to measure colored substances is called visible spectrophotometry.

[0005] 3. Determining the concentration of a certain solution by hydrometer method. There are two types of hydrometers: one is called a heavy scale, which is used to measure liquids heavier than water; the other is called a light scale, which is used to measure liquids lighter than water. After measuring the Baumé degree, the mass percentage concentration of the solution can be conveniently found from the corresponding conversion table in the chemical handbook. For example, when the Baumé degree of concentrated sulfuric acid measured at 15 °C is 6 °Bé, it can be found from the table that the mass percentage concentration of sulfuric acid is 98%. The Baumé degree value is relatively large and the reading is convenient, so the Baumé degree is commonly used to represent the concentration of the solution in production (a solution with a certain concentration has a certain density or specific gravity at a certain temperature). The measurement methods of the Baumé degree of different solutions are similar, all using the method of measuring specific gravity, and converting the concentration according to the measured specific gravity by looking up the table. Now there are special Baumé meters for different solutions, such as the alcohol Baumé meter and the brine Baumé meter. On these Baumé meters, there is the concentration of the corresponding type of solution corresponding to the measured Baumé degree of the solution, and the concentration can be directly read without looking up the table.

[0006] 4. Determination of the Concentration of a Solution by Polarimetry (Determination of the Concentration of a Chiral Substance Solution) In addition to depending on the stereostructure of the molecule to be measured, the magnitude of the optical rotation is also affected by factors such as the concentration of the solution to be measured, the thickness of the solution through which the polarized light passes (i.e., the length of the sample tube), as well as temperature, the wavelength of the light source used, and the solvent used. These factors must all be expressed in the measurement results. When a single plane-polarized light beam passes through a chiral substance, the direction of its vibration will change. At this time, the vibration plane of the light rotates by a certain angle. This phenomenon is called optical rotation.

[0007] 5. Online Concentration Sensor / Online Refractometer, which consists of a light source, a sapphire refraction unit, a light receiver, and a signal modulation circuit. The light source emits a stable light signal that passes through the sapphire and contacts the medium to be measured. The refractive index corresponding to the concentration of the medium to be measured is generated. The light receiver calculates the refractive index of the collected refracted light source and then obtains the corresponding concentration through a data algorithm. Since the concentration is affected by temperature, internal temperature calibration is adopted to reduce the influence of temperature drift.

[0008] The existing methods for measuring the concentration of transparent liquids have high measurement costs, complex operation processes, and expensive measurement equipment, which further increases the measurement cost.

[0009] Therefore, providing a method for measuring the concentration of transparent liquids with a simple operation method and accurate measurement has become a problem worthy of research. Summary of the Invention

[0010] The object of the present invention is to provide a method for measuring the concentration of transparent liquids with a simple operation method and accurate measurement.

[0011] The object of the present invention is achieved as follows:

[0012] A method for measuring the concentration of a transparent liquid, comprising the following steps:

[0013] Step 1: Prepare experimental equipment;

[0014] Step 2: Prepare four-necked flasks of the same specification, labeled flask 1, flask 2, and flask 3; Add a certain amount of distilled water to flask 1, and heat flask 1 to measure the boiling point elevation constant K value of the solvent using a temperature sensor and a humidity sensor. Then add a certain amount of distilled water to flask 2, and add a saturated NaCl solution equal in amount to the distilled water to flask 3;

[0015] Step 3: Heat flask 2 and flask 3, and at the same time place the temperature sensor and the humidity sensor into flask 2 and flask 3, and transmit the data to the display. Wait until the solutions in flask 2 and flask 3 boil, and record the temperatures of the two flasks at this time as Tb* and Tb respectively;

[0016] Step 4: According to Raoult's empirical formula ΔTb = Tb - Tb* = Kb * m, where Kb is the boiling point elevation constant of the solvent and relevant data can be obtained by looking up, m is the molality of the dilute solution with the unit mol / kg, Tb* represents the boiling point temperature of the pure solvent, and Tb represents the boiling point temperature of the solution. Substitute the temperature T1 and the temperature Tb in Step 3 into Raoult's empirical formula ΔTb = Tb - Tb* = Kb * m to calculate ΔTb. Look up the boiling point elevation constant Kb of the solvent in the table and substitute it into the formula ΔTb = Kb * m, then m = , thus obtaining the molality m value of the dilute solution, and then perform unit conversion to convert the molality m of the dilute solution into the concentration value of the ordinary solution, that is, obtain the concentration of the transparent liquid.

[0017] Step 5: Conduct multiple experiments, and take the average value of the concentration data of the transparent liquid from the multiple experimental data;

[0018] Step 6: Conduct water replenishment measurement, repeat Step 3, and adjust different water replenishment rates at different temperatures to ensure that the measured concentration of the transparent liquid remains unchanged.

[0019] In Step 6, install a straight condenser at the top of the four-neck flask, insert a thermometer and a hygrometer into the four-neck flask, use the data measured by the hygrometer and the thermometer, calculate the mass change rate according to the temperature gradient, thereby calculate the escaped moisture, and conduct artificial replenishment.

[0020] In Step 6, the humidity gradient relationship can be obtained (1)

[0021] where S is the cross-sectional area of the inner tube of the condenser , is the humidity near the flask end, is the humidity at the far end of the flask, L is the length of the condenser, K = K(T, S0, v), where T is the temperature, S0 is the surface area of the liquid in contact with air, and v is the air flow rate; keep S and v constant during the experiment;

[0022] (2)

[0023] (3)

[0024] is the saturated humidity of air corresponding to the temperature, is the air density, V is the air volume in the condenser, Δt is the heating time, and ΔH is the humidity change after distilled water; thus, a K-T image can be obtained, and substituting it into Equation (1) can obtain the moisture escape rate at different temperatures. At this time, control the separatory funnel to replenish water, and the separatory funnel controls its working state through a controller.

[0025] Positive beneficial effects: The present invention measures the concentration of a colorless and transparent liquid by utilizing the change in the boiling point of the solution. After the water replenishment operation is adopted, the dissipated water can be directly replenished, thereby reducing the measurement error and avoiding the phenomenon that the solution concentration changes significantly due to the heating intensifying the solvent vaporization when using Raoult's law to measure the concentration by boiling point; the measuring device is simple, easy to operate, has high measuring accuracy, and low single measurement cost. Brief Description of the Drawings

[0026] Figure 1 It is the K value diagram of the present invention at different temperatures;

[0027] Figure 2 It is the comparison diagram of the present invention without water replenishment operation, water replenishment operation and the standard value. Embodiment

[0028] The present invention will be further described below in conjunction with the drawings and embodiments.

[0029] A method for measuring the concentration of a transparent liquid includes the following steps:

[0030] Step 1: Prepare experimental equipment.

[0031] Step 2: Prepare four-neck flasks with the same specifications, label the flasks as flask 1, flask 2 and flask 3; add a certain amount of distilled water to flask 1, heat flask 1 and use a temperature sensor and a humidity sensor to measure the solvent boiling point elevation constant K value, then add a certain amount of distilled water to flask 2, and add a saturated Nacl solution equal in amount to the distilled water to flask 3.

[0032] Step 3: Heat flask 2 and flask 3, and at the same time put the temperature sensor and the humidity sensor into the two flasks 2 and 3, and transmit the data to the display. Wait until the solutions in flask 2 and flask 3 boil, and record the temperatures of the two flasks at this time as Tb* and Tb respectively.

[0033] Step 4: According to Raoult's empirical formula ΔTb = Tb - Tb* = Kb*m, where Kb refers to the solvent boiling point elevation constant, relevant data can be found, m refers to the molality of the dilute solution, unit mol / kg, where Tb* represents the boiling point temperature of the pure solvent, Tb represents the boiling point temperature of the solution, then substitute the temperature Tb* and the temperature Tb in step 3 into Raoult's empirical formula ΔTb = Tb - Tb* = Kb*m, calculate ΔTb, obtain the solvent boiling point elevation constant Kb by looking up the table, and substitute it into the formula ΔTb = Kb*m, then m = , thereby obtaining the molality m value of the dilute solution, and then performing unit conversion to convert the molality m of the dilute solution into the concentration value of the ordinary solution, that is, obtaining the concentration of the transparent liquid.

[0034] Step 5: Conduct multiple experiments, and take the average of the concentration data of the transparent liquid from multiple experimental data.

[0035] Step 6: Conduct water replenishment measurement. Repeat Step 3 and adjust different water replenishment rates at different temperatures to ensure that the measured concentration of the transparent liquid remains unchanged. After the water replenishment operation is adopted, the dissipated water can be directly replenished, thereby reducing the measurement error and avoiding the phenomenon that the solution concentration changes significantly due to the intensified vaporization of the solvent during the measurement of the concentration using the boiling point in Raoult's law.

[0036] In Step 6, install a straight condenser at the top of the four-neck flask, that is, use the straight condenser to reflux and collect the water vapor. The straight condenser condenses the water vapor and makes it reflux, thereby reducing the change in the solution concentration; insert the thermometer and hygrometer into the four-neck flask, and calculate the mass change rate according to the temperature gradient using the data measured by the hygrometer and thermometer, so as to calculate the dissipated water and make artificial replenishment.

[0037] Available from the humidity gradient relationship (1)

[0038] In the formula, S is the cross-sectional area of the inner tube of the condenser, , is the humidity near the flask end, is the humidity at the far end of the flask, L is the length of the condenser, K = K(T, S0, v), where T is the temperature, S0 is the surface area of the liquid in contact with the air, and v is the air flow rate; keep S and v unchanged during the experiment;

[0039] (2)

[0040] (3)

[0041] is the saturated humidity of the air corresponding to the temperature, is the air density, V is the air volume in the condenser, Δt is the heating time, and ΔH is the humidity change after distilled water; therefore, a K-T image can be obtained, and substituting it into Equation (1) can obtain the water dissipation rate at different temperatures. At this time, control the separatory funnel to replenish water, and the separatory funnel controls its working state through a controller.

[0042] Experimental data processing

[0043] When processing the experiment, the standard value of the Nacl solution concentration is 4.609 mol / kg.

[0044] 1. K-T table

[0045]

[0046] Table 1 Measuring the concentration of Nacl solution without water replenishment

[0047]

[0048] Table 2 Measuring the concentration of Nacl solution when using the water replenishment method

[0049]

[0050] Analysis of experimental results:

[0051] From Table 1 and Table 2, Figure 1 and Figure 2 it can be seen that when no water replenishment measures were taken, the measured value was 5.2015 mol / kg, which differed from the standard value of 4.609 mol / kg by 0.5925 mol / kg, and the relative error was 12.9%; after using the water replenishment measures, the measured value was 4.6449 mol / kg, which differed from the standard value by 0.0359 mol / kg, and the relative error was 0.7%. After replenishing water during the experimental process in the present invention, the measurement error is reduced and the detection accuracy is high.

[0052] The present invention measures the concentration of a colorless and transparent liquid by utilizing the change in the boiling point of the solution. After adopting the water replenishment operation, it can directly supplement the escaped water, thereby reducing the measurement error and avoiding the phenomenon that the solution concentration changes significantly due to the heating accelerating the vaporization of the solvent when using Raoult's law to measure the concentration by boiling point; the measuring device is simple, easy to operate, has high measurement accuracy, and low single - measurement cost.

Claims

1. A method for measuring the concentration of a transparent liquid, characterized in that: It includes the following steps: Step 1: Prepare the experimental equipment; Step 2: Prepare four-necked flasks with the same specifications, labeled Flask 1, Flask 2, and Flask 3; Add a certain amount of distilled water to Flask 1, heat Flask 1, and use a temperature sensor and a humidity sensor to measure the solvent boiling point elevation constant K value. Then add a certain amount of distilled water to Flask 2 and add a saturated NaCl solution equal in amount to the distilled water to Flask 3; Step 3: Heat Flask 2 and Flask 3, at the same time put the temperature sensor and the humidity sensor into Flask 2 and Flask 3, and transmit the data to the display. Wait until the solutions in Flask 2 and Flask 3 boil, and record the temperatures of the two flasks at this time as Tb* and Tb respectively; Step 4: According to Raoult's empirical formula ΔTb = Tb - Tb* = Kb * m, where Kb refers to the boiling point elevation constant of the solvent, relevant data can be obtained by looking up, m refers to the molality of the dilute solution, with the unit mol / kg, Tb* represents the boiling point temperature of the pure solvent, and Tb represents the boiling point temperature of the solution. Then substitute the temperature Tb* and the temperature Tb in Step 3 into Raoult's empirical formula ΔTb = Tb - Tb* = Kb * m to calculate ΔTb. By looking up the table, obtain the boiling point elevation constant Kb of the solvent and substitute it into the formula ΔTb = Kb * m, then m = , thus obtaining the value of the molality m of the dilute solution, and then perform unit conversion to convert the molality m of the dilute solution into the concentration value of the ordinary solution, that is, obtain the concentration of the transparent liquid; Step 5: Conduct multiple experiments, and take the average value of the concentration data of the transparent liquid from the multiple experimental data; Step 6: Conduct water replenishment measurement, repeat Step 3, and adjust different water replenishment rates at different temperatures to ensure that the concentration of the measured transparent liquid remains unchanged.

2. The method for measuring the concentration of a transparent liquid according to claim 1, wherein: In Step 6, install a straight condenser at the top of the four-necked flask, insert a thermometer and a hygrometer into the four-necked flask, calculate the mass change rate according to the temperature gradient based on the measurement data using the hygrometer and the thermometer, thereby calculate the escaped moisture, and conduct artificial replenishment.

3. The method for measuring the concentration of a transparent liquid according to claim 2, wherein: In the said step 6, the humidity gradient relationship can be obtained (1) where S is the cross-sectional area of the inner tube of the condenser, , is the humidity near the bottle end, is the humidity far from the bottle end, L is the length of the condenser, K = K(T, S0, v), where T is the temperature, S0 is the surface area of the liquid in contact with air, and v is the air flow rate; S and v are kept constant in the experiment; （2） （3） is the saturated humidity of air corresponding to the temperature, is the air density, V is the air volume in the condenser tube, Δt is the heating time, and ΔH is the humidity change after distilled water; thus, a K-T image can be obtained and substituted into Equation (1) to obtain the water evaporation rate at different temperatures. At this time, the separating funnel is controlled to replenish water, and the separating funnel controls its working state through a controller.

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