Absolute measurement method and device for density of fused salt and solution

Abstract

The invention discloses an absolute measurement method and device for the density of molten salt and solution, and belongs to the field of molten salt physical property tests.The measurement method comprises the steps that 1, a cone and cylinder composite heavy hammer is adopted to measure the density of the molten salt or solution; 2) arranging two measuring positions on the cylinder section of the heavy punch, taking the section between the two measuring positions as a middle measuring section, the length of the middle measuring section is equal to the distance between the two measuring positions, the diameter of the middle measuring section is equal to the diameter of the cylinder of the heavy punch, and measuring at the two positions in sequence; (3) the density of the fused salt or the solution is determined by the volume of the middle measuring section of the heavy hammer and the buoyancy borne by the middle measuring section, so that the density of the fused salt and the solution is deduced; according to the method, a long-distance microscope system is adopted to directly measure the thermal expansion of the heavy hammer at high temperature, calibration by a standard substance is not needed any more, when the method is adopted to measure the density of the fused salt and the solution, the volume of the heavy hammer does not need to be calibrated, additional force caused by surface tension is completely removed, the measurement process is greatly simplified, and the measurement precision is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of molten salt physical property testing, and particularly relates to an absolute measurement method and device for molten salt and solution density. BACKGROUND

[0002] The absolute measurement method for high-temperature molten salt density is based on the "direct Archimedes method". When the principle of the "Archimedes method" is applied to measure the density of molten salt or solution, the weight as a measuring element needs to be immersed in the molten salt or solution. In this process, the volume of the weight and the buoyancy of the weight after being immersed in the molten salt or solution are measured, and then the density of the molten salt or solution is obtained. However, in actual measurement, the shape of the weight is not a simple geometric body, and the volume of the weight changes due to thermal expansion at high temperature. Therefore, the volume of the weight is generally measured indirectly by calibration, and there is no report on direct measurement of the volume of the weight. For example, the volume of the weight at room temperature is calibrated by using a standard water solution, and then the volume of the weight at high temperature is calculated by using the thermal expansion coefficient of the weight material. This method for measuring the density of molten salt belongs to relative measurement, and needs to be improved. The calibration is also a measurement process, which makes it necessary to have two almost identical operation processes for measuring the density of molten salt or solution once, and is not simple enough. If the volume of the weight, especially the volume of the weight at high temperature, can be directly measured simply, the process of calibrating the volume of the weight can be omitted, the measurement process can be greatly simplified, and the absolute measurement of the density of molten salt can be realized.

[0003] The utility model patent with the authorized announcement number CN 209460096U calibrates the volume of the platinum weight at room temperature by using air and water, and does not describe the correction of the thermal expansion of the platinum weight at high temperature when measuring the density of molten salt;

[0004] The utility model patent with the authorized announcement number CN209132122U measures the density of molten salt by using the "direct Archimedes method", and does not describe the thermal expansion of the weight at high temperature and the processing method in the technical solution. If the influence of the thermal expansion of the weight is ignored, the obtained data cannot meet the requirements of scientific research. SUMMARY

[0005] In view of the problem that the volume of the weight, especially the volume of the weight at high temperature, needs to be calibrated by using a standard substance in the method for measuring the density of molten salt and solution based on the principle of the "Archimedes method", the application provides an absolute measurement method and device for the density of molten salt and solution, which directly measures the density of molten salt or solution without calibrating the volume of the weight.

[0006] To achieve the above object, the technical scheme adopted by the application is as follows:

[0007] The heavy hammer of the present application is used to replace the traditional spherical heavy hammer and spindle-shaped heavy hammer. The spindle-shaped heavy hammer given in the document Metallurgical Physical Chemistry Research Method edited by Wang Changzhen and the heavy hammer used in the present application are shown in Figure 1 , which is a kind of conical and cylindrical composite heavy hammer. The method of the present application sets two measuring positions in the cylindrical section of the heavy hammer, so the cylindrical section of the traditional spindle-shaped heavy hammer is lengthened to form a new-shaped heavy hammer. The heavy hammer used in the present application is composed of three parts. The main body of the heavy hammer is a long cylinder in the middle part, with a diameter of 5-10 mm and a length of 3-8 times of the diameter, so as to facilitate the measurement of the high-temperature volume of the heavy hammer. The lower part of the heavy hammer is a conical body, which functions to avoid the adsorption of bubbles at the bottom of the heavy hammer. The upper part of the heavy hammer is a suspension structure.

[0008] Two measuring positions are set in the cylindrical section of the heavy hammer, as shown in Figure 1 B. The first measuring position is the position where the front end of the cylindrical section of the heavy hammer is shallowly immersed in the melt and meets the liquid surface. The balance reading at this position is P1. The second measuring position is the position where the cylindrical section of the heavy hammer is positioned at a deeper position 5-30 mm below the first measuring position after being accurately controlled by the linear module. The balance reading at this position is P2. The section between the two measuring positions is the middle measuring section of the heavy hammer, with a diameter equal to the diameter of the cylindrical section of the heavy hammer and a length equal to the sum of the sinking distance h of the heavy hammer from the first measuring position and the liquid surface rising Δh caused by the sinking of the heavy hammer, i.e. H = h + Δh.

[0009] The density of the molten salt or solution is determined by the volume V t of the middle measuring section of the heavy hammer and the buoyancy f of the middle measuring section. The volume of the middle measuring section of the heavy hammer at high temperature is:

[0010]

[0011] The buoyancy of the middle measuring section in the melt is f = P1-P2, and the calculation formula of the density ρ of the molten salt is obtained as follows:

[0012]

[0013] In formula (1), π is the circular constant, H is the length of the middle measuring section of the heavy hammer, d t is the diameter of the middle measuring section at the measuring temperature, and D t is the inner diameter of the crucible at the measuring temperature. In formula (2), P1-P2 makes the additional force p' caused by the surface tension, which is originally contained in P2 and P1, be subtracted, i.e. the influence is completely eliminated. Moreover, the filament connecting the upper suspension structure of the heavy hammer is not immersed in the molten salt or solution during the measurement, so the influence of the filament is completely eliminated.

[0014] In the above method, the diameter of the middle measuring section of the weight and the inner diameter of the crucible used are measured at room temperature using a digital micrometer, and at high temperature using a long-distance microscope system.

[0015] In the above method, when measuring the diameter of the middle measuring section of the weight, first aim at one edge of the weight using a long-distance microscope and record the position data M of the slider on the linear guide support; then drive the slider to translate so that the long-distance microscope aims at the other edge of the weight and record the position data N of the slider. The diameter of the weight is then d. t =|MN|.

[0016] The high-temperature inner diameter measurement of the crucible is the same as the high-temperature diameter measurement of the weight.

[0017] In the above method, the material of the weight used is one of platinum, platinum alloy, or molybdenum.

[0018] In the above method, when measuring the density of the solution, the diameter d of the middle measuring section of the weight and the inner diameter D of the crucible are measured with a digital micrometer, and then the density of the solution is calculated according to the above formula.

[0019] The technical solution of this invention transforms the volume measurement of a weight into the diameter measurement of its cylindrical segment, thereby achieving direct measurement of the volume of the weight's measuring segment without the need for calibration with standard substances, and realizing absolute measurement of the density of molten salt and solution. Since the calibration process for the weight's volume is eliminated, and the additional force caused by surface tension can be completely removed, this method for absolute measurement of the density of molten salt or solution simplifies the measurement process and improves measurement accuracy.

[0020] The measuring device provided by the present invention is as follows: Figure 2 As shown: An absolute measuring device for the density of molten salt and solution includes a balance 1, a balance platform 2, a fine wire 3, a high-temperature furnace 4, a weight 5, a crucible 6, molten salt or solution 7, a furnace platform 8, a base 9, a servo motor 10, a linear module 11, a slide table 12, and a track 13.

[0021] The base 9, furnace platform 8 and linear module 11 together form a stable equipment support, wherein the furnace platform 8 is fixed on the base 9, and the linear module 11 stands vertically on the base and is fixed to the furnace platform 8.

[0022] The linear module 11 includes a component servo motor 10, a slide table 12, and a track 13. The servo motor 10 drives the slide table 12 to move up and down along the track 13.

[0023] The high-temperature furnace 4 is placed on the furnace platform 8, directly below the balance platform 2; the crucible 6 is placed inside the high-temperature furnace 4;

[0024] The balance platform 2 is fixed on the slide table 12 of the linear module 11 and can be lifted and positioned by the slide table 12; the balance 1 is placed on the balance platform 2 and moves with the balance platform 2.

[0025] One end of the filament 3 is connected to the lower hook of the balance 1, and the other end is connected to the weight 5; the weight 5 is suspended above the high-temperature furnace 4 by the filament 3 and is driven by the balance 2 to sink into the molten salt or solution 7 in the crucible 6.

[0026] In the technical solution of this invention, the diameter of the weight and the inner diameter of the crucible need to be determined in advance, measured using a digital micrometer at room temperature and a long-distance microscope system at high temperature. Figure 3 As shown, the long-distance microscope system includes: a long-distance microscope 14, a computer 15, a quartz glass window 16, a linear guide rail support 17, a microscope adjustment support 18, a sample tube 19, and a weight positioning frame 20.

[0027] The long-distance microscope 14 is fixed on the microscope adjustment bracket 18, which is fixed on the slider of the linear guide rail bracket 17. The counterweight positioning frame 20 is placed inside the sample tube 19, and the counterweight 5 is inserted into the counterweight positioning frame 20. The long-distance microscope 14 and the computer 15 transmit data through a data port. During measurement, the long-distance microscope system is installed on the furnace mouth of the high-temperature furnace 4, and its sample tube 19 is hung on the furnace mouth with the tube body embedded in the furnace chamber. The axis of the long-distance microscope 14 is coaxial with the axis of the sample tube 19.

[0028] The absolute measurement method for the density of molten salt or solution of the present invention comprises the following measurement steps:

[0029] 1. When measuring the density of molten salt, the diameter d of the cylindrical section of the weight at each high-temperature measurement point is measured beforehand using a long-distance microscope system. t For use during measurement; when measuring the density of a solution, measure the diameter d of the cylindrical section of the weight using a digital micrometer at room temperature;

[0030] 2. When measuring the density of molten salt, the diameter D of the crucible at each high-temperature measurement point is measured beforehand using a long-distance microscope system. t For use during measurement; when measuring the density of a solution, measure the inner diameter D of the crucible with a digital micrometer at room temperature;

[0031] 3. When measuring the density of molten salt, an accurate measurement of the high-temperature inner diameter D was used. t The crucible is filled with molten salt sample and sent into a high-temperature furnace to melt; when measuring the density of the solution, the crucible to be tested is filled with a crucible whose room temperature inner diameter D is accurately measured, and the furnace mouth is used as the sample stage, and the crucible is placed on the sample stage.

[0032] 4. The high-temperature diameter d of the cylindrical section was accurately measured. tOr a weight of diameter d at room temperature is suspended from the lower hook of the balance;

[0033] 5. Use the linear module to precisely control the descent of the balance platform, causing the weight to be immersed in molten salt or solution. When the cylindrical section of the weight is shallowly immersed in the molten salt or solution for positioning, the junction between the liquid surface and the cylindrical section of the weight is the first measurement position. The balance reading measured at this measurement position is P1.

[0034] 6. Continue to control the balance platform to descend using the linear module, causing the weight to sink from the first measuring position to a deeper position. At this point, the junction between the liquid surface and the cylindrical section of the weight is the second measuring position. The balance reading at this measuring position is P2.

[0035] 7. When measuring the density of molten salt, calculate the volume of the middle measuring section of the weight using the following formula:

[0036]

[0037] When measuring the density of a solution, calculate the volume of the middle measuring section of the weight using the following formula:

[0038]

[0039] 8. Calculate the buoyancy force on the intermediate measuring section of the weight in the melt or liquid using the following formula:

[0040] f = P1 - P2

[0041] 9. When measuring the density of molten salt, calculate the density ρ of the molten salt using the following formula:

[0042]

[0043] When measuring the density of a solution, the density ρ of the solution is calculated using the following formula:

[0044]

[0045] In the above calculation formula, H is the length of the middle measuring section of the weight, and d is the room temperature diameter of the middle measuring section. t D is the diameter of the intermediate measuring section at the measuring temperature, and D is the room temperature inner diameter of the crucible. t P1 is the inner diameter of the crucible at the measurement temperature, P2 is the balance reading measured at the first measurement position, and P3 is the balance reading measured at the second measurement position.

[0046] Key points of this invention:

[0047] In the method of this invention, as long as the first and second measuring positions are both on the cylindrical section of the weight, the measurement results will be the same. Although the distance between the measuring positions differs, resulting in different buoyant forces, the density calculated according to the formula remains the same.

[0048] The beneficial effects of this invention are:

[0049] This invention discloses an absolute measurement method and apparatus for the density of molten salts and solutions. The method involves using a composite weight consisting of a cone and a cylinder to measure the density of the molten salt or solution. The length of the central cylindrical section of the weight is 3 to 8 times its diameter to facilitate the measurement of the weight's high-temperature volume. Two measurement positions are set within the cylindrical section of the weight, with the section between these two positions being the intermediate measurement section. The length of this section is the distance between the two measurement positions, and its diameter is the diameter of the cylindrical weight. Measurements are performed sequentially at these two positions. The density of the molten salt or solution is determined by the volume V of the intermediate measurement section of the weight and the buoyancy f acting on it. A long-distance microscope system is used to directly measure the thermal expansion of the weight at high temperatures, eliminating the need for calibration with standard materials. When measuring the density of molten salts and solutions using the method provided by this invention, it is unnecessary to calibrate the weight's volume, and the additional force caused by surface tension can be completely eliminated, greatly simplifying the measurement process and improving measurement accuracy. Attached Figure Description

[0050] Figure 1 Schematic diagram of the weight; A is a disclosed weight, and B is the weight disclosed in this invention;

[0051] Figure 2 Schematic diagram of an absolute measuring device for molten salt and solution density;

[0052] Figure 3 Schematic diagram of high-temperature diameter measurement method for a weight;

[0053] In the diagram, 1. Balance, 2. Balance platform, 3. Wire, 4. High-temperature furnace, 5. Weight, 6. Crucible, 7. Molten salt or solution, 8. Furnace platform, 9. Base, 10. Servo motor, 11. Linear module, 12. Slide table, 13. Track, 14. Long-distance microscope, 15. Computer, 16. Quartz glass window, 17. Linear guide rail support, 18. Microscope adjustment support, 19. Sample tube, 20. Weight positioning frame. Detailed Implementation

[0054] An absolute measuring device for the density of molten salts and solutions, such as Figures 1-3 As shown, it includes a balance 1, a balance platform 2, a fine wire 3, a high-temperature furnace 4, a weight 5, a crucible 6, molten salt or solution 7, a furnace platform 8, a base 9, a servo motor 10, a linear module 11, a slide table 12, a track 13, a long-distance microscope 14, a computer 15, a quartz glass window 16, a linear guide rail bracket 17, a microscope adjustment bracket 18, a sample tube 19, and a weight positioning frame 20.

[0055] The base 9, furnace platform 8 and linear module 11 together form a stable equipment support, wherein the furnace platform 8 is fixed on the base 9, and the linear module 11 stands vertically on the base and is fixed to the furnace platform 8.

[0056] The linear module 11 includes a component servo motor 10, a slide table 12, and a track 13. The servo motor 10 drives the slide table 12 to move up and down along the track 13.

[0057] The high-temperature furnace 4 is placed on the furnace platform 8, directly below the balance platform 2; the crucible 6 is placed inside the high-temperature furnace 4;

[0058] The balance platform 2 is fixed on the slide table 12 of the linear module 11 and can be lifted and positioned by the slide table 12; the balance 1 is placed on the balance platform 2 and moves with the balance platform 2.

[0059] One end of the thin wire 3 is connected to the lower hook of the balance 1, and the other end is connected to the weight 5; the weight 5 is suspended above the high-temperature furnace 4 by the thin wire 3, and is driven by the balance 2 to sink into the molten salt or solution 7 in the crucible 6.

[0060] The weight 5 consists of three parts: the main body of the weight is a long cylinder in the middle, with a diameter of 5-10 mm and a length that is 3-8 times its diameter; the lower part of the weight is a cone, which is used to prevent air bubbles from adsorbing at the bottom of the weight; the upper part of the weight is a suspension structure, which is connected to the lower hook of the balance 1 by a thin wire; two measuring positions are set on the cylindrical section of the weight. The first measuring position is the position where the cylindrical section of the weight is shallowly immersed in the melt / solution and meets the liquid surface, and the balance reading is measured at this position as P1; the second measuring position is the position where the cylindrical section of the weight meets the liquid surface after sinking 5-30 mm from the first measuring position to a deeper position, and the balance reading is measured at this position as P2.

[0061] The long-distance microscope 14 is fixed on the microscope adjustment bracket 18, which is fixed on the slider of the linear guide rail bracket 17. The counterweight positioning frame 20 is placed inside the sample tube 19, and the counterweight 5 is inserted into the counterweight positioning frame 20. The long-distance microscope 14 and the computer 15 transmit data through a data port. During measurement, the long-distance microscope system is installed on the furnace mouth of the high-temperature furnace 4, and its sample tube 19 is hung on the furnace mouth with the tube body embedded in the furnace chamber. The axis of the long-distance microscope 14 is coaxial with the axis of the sample tube 19.

[0062] Example 1: Measurement of the density of anhydrous ethanol

[0063] Measuring equipment: The sample is contained in a graphite crucible, the fine wire is made of molybdenum wire, and the weight is made of molybdenum.

[0064] Balance: Use Sartorius balance BSA223S with a lower hook;

[0065] The linear module is Shengkai Transmission SCH136B2-0.5T-400-SC-YX;

[0066] The inner diameter of the graphite crucible was measured with calipers; D = 42.21 mm.

[0067] The diameter of the middle measuring section of the weight is measured with calipers, and d = 10.06 mm.

[0068] Pour anhydrous ethanol into the crucible, and then place the crucible on the sample platform;

[0069] The temperature of the anhydrous ethanol solution was measured to be 23 degrees Celsius.

[0070] Place the balance scale on the platform;

[0071] The weight is secured with a thin wire, the other end of which is attached to the lower hook of the balance, so that the weight is suspended directly above the crucible.

[0072] Start the linear module and control the platform to descend, immersing the counterweight in anhydrous ethanol solution to a depth of 5mm, and let it stand for 10 seconds.

[0073] Read the data from the balance at this moment and record it as P1;

[0074] The weight is precisely lowered by 20mm, i.e., H = 20mm;

[0075] Read the data from the balance at this moment and record it as P2;

[0076] Substitute the data into the formula Calculate the density of the anhydrous ethanol solution;

[0077] Repeat the above procedure three times. The measurement results are as follows:

[0078] ①P1=34.996g, P2=33.343g, ρ=0.7858g / cm 3 ;

[0079] ②P1=34.785g, P2=33.790g, ρ=0.7871g / cm 3 ;

[0080] ③P1=34.782g, P2=33.459g, ρ=0.7849g / cm 3 ;

[0081] The average of the three measurements yielded a density of anhydrous ethanol of 0.7859 g / cm³ at 23 degrees Celsius. 3 The standard value for anhydrous ethanol at 23 degrees Celsius is ρ = 0.7869 g / cm³. 3 Therefore, the measurement error of the present invention is 0.13%, which fully meets the requirements of high-precision measurement.

[0082] Example 2: Measurement of the density of NaCl (801℃)

[0083] Measuring supplies: The crucible is made of high-purity graphite, the wire is made of platinum wire, and the weight is made of platinum.

[0084] Balance: A Sartorius balance with a lower hook is used;

[0085] The inner diameter of the graphite crucible at 801℃ is: D 801 =50.122mm;

[0086] Measure the diameter d of the weight at 801℃. 801 =10.18mm;

[0087] Solid NaCl powder is loaded into a graphite crucible and then placed in a high-temperature furnace to melt.

[0088] Place the balance scale on the platform;

[0089] The weight is attached by a thin wire, with the other end of the wire attached to the lower hook of the balance, so that the weight is suspended directly above the crucible; after NaCl melts, the temperature of the melt is controlled to be kept constant at 801℃.

[0090] Start the linear module to control the platform to descend, so that the weight is immersed in the NaCl melt to a depth of 10mm;

[0091] Read the data from the balance at this moment and record it as P1;

[0092] The weight is precisely lowered by 20mm, i.e., H = 20mm;

[0093] Read the data from the balance at this moment and record it as P2;

[0094] Substitute the data into the formula Calculate the density of the NaCl melt;

[0095] Measurement result: ρ = 1.546 g / cm³ 3 The standard value is ρ = 1.556 g / cm³. 3 The error is 0.64%.

Claims

1. A method for absolute measurement of the density of molten salt and solution, characterized in that, include: 1) The weight used consists of three parts: the main body of the weight is a long cylinder in the middle; the lower part of the weight is a cone, which is used to prevent air bubbles from being attracted to the bottom of the weight; and the upper part of the weight is a suspension structure. 2) Pre-measure the diameter d of the long cylindrical section of the weight at the test temperature. t and the inner diameter D of the crucible used at the test temperature t ; 3) Set up two measuring positions in the long cylindrical section of the weight. During measurement, first immerse the front end of the long cylindrical section of the weight into molten salt or solution. The position where the liquid surface meets the weight is the first measuring position. Measure the balance reading P1 at the first measuring position. Then, continue to sink the weight 5-30 mm from the first measuring position to a fixed position. The position where the liquid surface meets the weight is the second measuring position. Measure the balance reading P2 at this position. 4) The section from the first measuring position to the second measuring position of the weight is the intermediate measuring section. The density of the molten salt is determined by the volume V of the intermediate measuring section at high temperature. t The volume of the intermediate measuring section of the weight is determined by the buoyancy force f acting on it; the volume of the intermediate measuring section of the weight at high temperature is: The buoyancy force on the middle measuring section of the hammer in the melt is: f = P1 - P2; Therefore, the formula for calculating the density ρ of molten salt is: In the formula, π is the mathematical constant Pi, H is the length of the middle measuring section of the weight, and d t D is the diameter of the intermediate measurement section at the measurement temperature. t P1-P2 is the inner diameter of the crucible at the measurement temperature; P1-P2 is the additional force p caused by surface tension that was originally included in P2 and P1. , It is subtracted, meaning its effect is completely eliminated; 5) When measuring the density of the solution, use a digital micrometer to measure the diameter d of the middle measuring section of the weight and the inner diameter D of the crucible, and then calculate the density of the solution according to the formula in step 4).

2. The absolute measurement method for the density of molten salt and solution according to claim 1, characterized in that, The long cylindrical part of the hammer used has a diameter of 5 to 10 mm and a length that is 3 to 8 times its diameter.

3. The absolute measurement method for the density of molten salt and solution according to claim 1, characterized in that, The diameter d of the long cylindrical weight was measured beforehand using a long-distance microscope system at the measurement temperature. t and the inner diameter D of the crucible t .

4. The absolute measurement method for the density of molten salt and solution according to claim 3, characterized in that, When measuring the diameter of the long cylindrical weight, first aim at one edge of the long cylindrical weight using a long-distance microscope and record the position data M of the slider on the linear guide support; then drive the slider to translate so that the long-distance microscope aims at the other edge of the long cylindrical weight and record the position data N of the slider. The diameter of the long cylindrical weight section at the measurement temperature is then: d t =|MN|; the inner diameter D of the crucible at the measurement temperature. t Measure using the same method.

5. The absolute measurement method for the density of molten salt and solution according to claim 1, characterized in that, The section between the two measurement positions is the intermediate measurement section, the length of which is determined by the sinking distance h of the weight from the first measurement position and the rise in liquid level Δh caused by the sinking of the weight, i.e., H = h + Δh; measurements are taken sequentially at the two measurement positions.

6. An absolute measuring device for molten salt and solution density, used to implement the absolute measuring method for molten salt and solution density as described in claim 1, characterized in that, Includes balance (1), balance platform (2), filament (3), high temperature furnace (4), weight (5), crucible (6), furnace platform (8), base (9), servo motor (10), linear module (11), slide table (12), track (13), long distance microscope (14), computer (15), quartz glass window (16), linear guide rail bracket (17), microscope adjustment bracket (18), sample tube (19), and weight positioning frame (20); The base (9), furnace platform (8) and linear module (11) together form a stable equipment support, wherein the furnace platform (8) is fixed on the base (9) and the linear module (11) stands vertically on the base and is fixed to the furnace platform (8). The high-temperature furnace (4) is placed on the furnace platform (8), directly below the balance platform (2); the crucible (6) is placed inside the high-temperature furnace (4); The balance platform (2) is fixed on the slide table (12) of the linear module (11) and is driven to rise and be positioned by the slide table (12); the balance (1) is placed on the balance platform (2) and moves up and down with the balance platform (2); One end of the filament (3) is connected to the lower hook of the balance (1), and the other end is connected to the weight (5); the weight (5) is suspended above the high-temperature furnace (4) by the filament (3), and is driven by the balance platform (2) to sink into the molten salt or solution in the crucible (6); The long-distance microscope (14) is fixed on the microscope adjustment bracket (18), the microscope adjustment bracket (18) is fixed on the slider of the linear guide bracket (17), the weight positioning frame (20) is placed inside the sample tube (19), the weight (5) is inserted into the weight positioning frame (20), and the long-distance microscope (14) and the computer (15) transmit data through the data port.

7. The absolute measuring device for molten salt and solution density according to claim 6, characterized in that, The hammer (5) consists of three parts: the main body of the hammer is a long cylinder in the middle with a diameter of 5-10 mm and a length that is 3-8 times the diameter; the lower part of the hammer is a cone, which is used to prevent air bubbles from being adsorbed at the bottom of the hammer; the upper part of the hammer is a suspension structure connected to the lower hook of the balance (1) by a thin wire; two measuring positions are set on the cylindrical section of the hammer. The first measuring position is the position where the front end of the cylindrical section of the hammer is immersed in the melt or liquid and meets the liquid surface. The balance reading at this position is P1; the second measuring position is the position where the cylindrical section of the hammer continues to sink from the first measuring position to the position where the rear end of the cylindrical section of the hammer meets the liquid surface. The balance reading at this position is P2.

8. The absolute measuring device for molten salt and solution density according to claim 6, characterized in that, During measurement, the long-distance microscope system is installed on the furnace mouth of the high-temperature furnace (4), the sample tube (19) is hung on the furnace mouth, and the tube body is embedded in the furnace chamber; the axis of the long-distance microscope (14) is coaxial with the axis of the sample tube (19).

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