Method for measuring boron content in boride

Abstract

The invention relates to a method for measuring the content of boron in a boride. The method specifically comprises the following steps: pretreating a boron-containing compound to obtain a solution to be titrated; titrating the solution to be titrated by using the alkaline titration solution, and measuring the pH value of the solution to be titrated and the volume of the alkaline titration solution in real time in the titration process; drawing a titration curve graph through EXCEL software, and fitting a first straight line; connecting points on two sides of an intersection point of the first straight line and the titration curve and extending to obtain a second straight line; the volume corresponding to the intersection point of the first straight line and the second straight line is the titration end point volume, and the boron content in the boride can be calculated through a formula. The determination method provided by the invention is simple, rapid and less in interference, and improves the accuracy and stability of the test.

Description

Technical Field

[0001] The invention belongs to the technical field of substance content testing, and in particular relates to a method for determining the boron content in a boride-containing substance. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance the understanding of the overall background of the invention and should not be necessarily regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] The traditional method for determining the boron content in boride is to use phenolphthalein as an indicator, utilize acid-base neutralization reaction, and confirm the reaction endpoint by observing the color change of the solution during titration. This method has two problems: ① Using phenolphthalein as an indicator for this reaction, its color change range is between 8.2 and 10.0, and the color will not change until the pH reaches 8. At this time, the volume of NaOH consumed will be significantly higher than the volume when the boric acid is completely reacted. At the same time, the color change range is within a certain range, resulting in frequent errors in the titration process; ② When the boron content is high, the solution color change is more obvious and the accuracy is higher, but when the boron content is low, the titration color change is not obvious, and it often occurs that when analyzing and measuring the same sample, the observation conclusions of different experimenters are quite different.

[0004] Compared with the traditional indicator method, the use of an acidometer to measure the solution reaction process can eliminate the influence of human subjective factors. Yang Xuefen et al. used an acidometer to determine the content of boron oxide in boron phosphate, taking pH = 6.3 as the titration starting point. After adding mannitol, the pH dropped, and then the solution was titrated to pH = 6.3 using alkaline solution. The repeatability of the test results was higher than that of the traditional indicator method. However, this method can only use a single pH value as the titration endpoint, and there is no basis for the selection of the titration endpoint. Therefore, it is of great significance to study a new method for determining the boron content and improve the accuracy of the determination. Summary of the invention

[0005] In view of the needs of the prior art, the purpose of the present invention is to provide a method for determining the boron content in boride-containing materials, which can achieve simple and rapid testing of element content with less interference in the testing process, high test accuracy and good stability.

[0006] Specifically, the present invention provides the following technical solutions:

[0007] A first aspect of the present invention provides a method for determining the boron content in a boride, comprising the following steps:

[0008] S1. Pretreating the boron-containing compound to obtain a solution to be titrated;

[0009] S2, titrating the solution to be titrated with an alkaline titration solution, and measuring the pH value of the solution to be titrated and the volume of the alkaline titration solution in real time during the titration process;

[0010] S3, drawing a titration curve and fitting a first straight line;

[0011] S4, connecting the points on both sides of the intersection of the first straight line and the titration curve and extending them to obtain a second straight line;

[0012] S5. The volume corresponding to the intersection of the first straight line and the second straight line is the titration endpoint volume. Based on the obtained titration endpoint volume, the boron content in the boride is calculated.

[0013] Preferably, in step S1, the pretreatment is to digest the boron-containing compounds.

[0014] Preferably, in step S2, the alkaline titration solution is selected from one of sodium hydroxide (NaOH) and potassium hydroxide (KOH); and the concentration of the titration solution is 0.01 mol / L to 0.2 mol / L.

[0015] Preferably, in step S2, the pH value of the solution to be titrated is measured using an MP230 acidity meter from Mettler Toledo. The acidity meter needs to be calibrated before use, that is, titration is performed with a titration solution of a determined concentration, and the pH corresponding to the titration volume is recorded with the acidity meter.

[0016] Preferably, in step S2, the pH value of the solution to be titrated is measured once every 20s to 40s.

[0017] Preferably, in step S2, the solution to be titrated is magnetically stirred during the titration process, and the stirring speed is 50 to 200 rpm.

[0018] Preferably, in step S3, the titration curve is drawn using EXCEL software, and the first straight line is fitted using EXCEL software; further preferably, the titration curve takes the volume of the alkaline titration solution as the abscissa and the pH value of the solution to be titrated as the ordinate.

[0019] Preferably, in step S3, the first straight line is y1=ax+b.

[0020] Preferably, in step S4, the second straight line is fitted using EXCEL software; the second straight line is y2=cx+d.

[0021] Preferably, in step S5, the first straight line has three intersection points with the titration curve.

[0022] Preferably, in step S5, the boron content in the boride is calculated according to the following formula (1)(2)(3):

[0023]

[0024] Where: B 2 O 3 B is the boron oxide content; 游离 is the free boron content; B 总 is the total boron content; C is the concentration of NaOH standard solution, in mol / L; V 0 is the volume of NaOH consumed by the blank, in mL; V is the volume of NaOH consumed by the sample, in mL; m is the mass of the sample, in g.

[0025] The beneficial effects achieved by the technical solution of the present invention are as follows:

[0026] The method for determining the boron content by the acidometer method of the present invention can eliminate the judgment of the titration end point by human subjective factors, the test result is accurate and reliable, and the accuracy of the determination of the boron content in the boride is improved. It is suitable for the determination of the total boron, boron oxide and free boron content in the boride. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0028] Figure 1 This is a titration curve diagram for detecting the content of boron oxide in boron nitride in Example 1 of the present invention;

[0029] Figure 2 This is a titration curve diagram for detecting the total boron content in boron nitride in Example 1 of the present invention;

[0030] Figure 3 This is a titration curve diagram for detecting the free boron content in boron nitride in Example 1 of the present invention. DETAILED DESCRIPTION

[0031] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0032] As mentioned above, the traditional method for determining the boron content in boride is to use phenolphthalein as an indicator, utilize acid-base neutralization reaction, and confirm the reaction end point by observing the solution color change during titration. This method has the problem that the volume of NaOH consumed is obviously higher than the volume when the boric acid is just completely reacted, and the color change range is within a certain range, resulting in frequent errors in the titration process; and when the boron content is low, the titration color change is not obvious, and it often occurs that when analyzing and determining the same sample, the observation conclusions of different experimenters are quite different. In addition, although the influence of human subjective factors can be eliminated by using an acidity meter to measure the solution reaction process, such methods can only use a single pH value as the titration end point, and the selection of the titration end point lacks a basis. Therefore, those skilled in the art are in urgent need of studying a new method for determining the boron content to improve the accuracy of the determination.

[0033] A first typical embodiment of the present invention provides a method for determining the boron content in a boride, comprising the following steps:

[0034] S1. Pretreating the boron-containing compound to obtain a solution to be titrated;

[0035] S2, titrating the solution to be titrated with an alkaline titration solution, and measuring the pH value of the solution to be titrated and the volume of the alkaline titration solution in real time during the titration process;

[0036] S3, drawing a titration curve and fitting a first straight line;

[0037] S4, connecting the points on both sides of the intersection of the first straight line and the titration curve and extending them to obtain a second straight line;

[0038] S5. The volume corresponding to the intersection of the first straight line and the second straight line is the titration endpoint volume. Based on the obtained titration endpoint volume, the boron content in the boride is calculated.

[0039] In one or more examples of this implementation mode, in step S1, the pretreatment is to digest the boron-containing compound.

[0040] In one or more examples of this implementation, in step S2, the alkaline titration solution is selected from one of sodium hydroxide (NaOH) and potassium hydroxide (KOH); and the concentration of the titration solution is 0.01 mol / L to 0.2 mol / L.

[0041] In one or more examples of this implementation, in step S2, the pH value of the solution to be titrated is measured using an MP230 acidity meter produced by Mettler Toledo. The acidity meter needs to be calibrated before use, that is, titration is performed with a titration solution of a determined concentration, and the pH corresponding to the titration volume is recorded with the acidity meter.

[0042] In one or more examples of this implementation mode, in step S2, the pH value of the solution to be titrated is measured once every 20s to 40s.

[0043] In one or more examples of this implementation mode, in step S2, the solution to be titrated is magnetically stirred during the titration process, and the stirring speed is 50-200 rpm.

[0044] In one or more embodiments of this implementation mode, in step S3, the titration curve is drawn using EXCEL software, and the first straight line is fitted using EXCEL software; further preferably, the titration curve uses the volume of the alkaline titration solution as the horizontal coordinate and the pH value of the solution to be titrated as the vertical coordinate.

[0045] In one or more examples of this implementation, in step S3, the first straight line is y1=ax+b.

[0046] In one or more examples of this implementation mode, in step S4, the second straight line is fitted using EXCEL software; the second straight line is y2=cx+d.

[0047] In one or more examples of this implementation mode, in step S5, the first straight line has three intersection points with the titration curve.

[0048] In one or more examples of this embodiment, in step S5, the boron content in the boride is calculated according to the following formula (1), (2), (3):

[0049]

[0050] Where: B 2 O 3 B is the boron oxide content; 游离 is the free boron content; B 总 is the total boron content; C is the concentration of NaOH standard solution, in mol / L; V 0 is the volume of NaOH consumed by the blank, in mL; V is the volume of NaOH consumed by the sample, in mL; m is the mass of the sample, in g.

[0051] The invention comprises the following steps: loading a solution to be titrated into a titration container, connecting a titration device and a pH measurement module to the titration container, dripping a titration solution into the titration container by the titration device for titration, measuring the pH value of the solution to be titrated in the titration container in real time by the pH measurement module during the titration process, outputting the measured pH value to a calculation module connected to the pH measurement module after the titration is completed, recording the received pH value and the volume of the corresponding titration solution, drawing a titration curve with the volume of the alkaline titration solution as the abscissa and the pH value of the solution to be titrated as the ordinate, and fitting a first straight line; connecting points on both sides of an intersection of the first straight line and the titration curve and extending the points to obtain a second straight line, wherein a volume corresponding to the intersection of the first straight line and the second straight line is the titration endpoint volume, and calculating the boron content in the boride by a formula.

[0052] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0053] Example 1 :

[0054] This embodiment provides a method for determining the content of boron oxide in boron nitride, comprising the following steps:

[0055] Step 1: Weigh 1 g of ERM-ED103 sample (accurate to 0.1 mg), dissolve it in 70°C hot water for 40 min, filter it while hot, collect the filtrate in a 500 mL conical flask, cool it with running water, transfer it to a three-necked flask, add 5 g of mannitol, and add a rotor.

[0056] Step 2: Calibrate the acidometer with a pH standard solution and titrate the solution to be tested with a 0.05 mol / L NaOH standard solution. Use the acidometer to measure the pH change of the solution, collect data every 30 seconds, and the titration curve uses the titration volume as the horizontal axis and the pH value as the vertical axis.

[0057] Step 3: After collecting 19 sets of data using the acidometer, use EXCEL software to draw a titration curve. Use EXCEL fitting software to fit the data into a straight line y1=0.0045x+6.3447.

[0058] Step 4: Find the intersection of the straight line and the titration curve through the picture. Here the straight line will have 3 intersections with the titration curve. Select the middle intersection, connect the points on both sides of the middle intersection and extend it to get another straight line, y2 = 0.0085x + 4.64, y1 and y2 intersect at one point (426, 8.26), that is, the titration endpoint volume is 426μL, and the titration endpoint pH is 8.26.

[0059] Step 5: By using formula (1), after deducting the blank sample volume of 46 μL, the boron oxide content is calculated. At this time, the boron oxide content in the corresponding boron nitride is 0.066%.

[0060] Example 2 :

[0061] This embodiment provides a method for determining the total boron content in boron nitride, comprising the following steps:

[0062] Step 1: Weigh 0.1 g (accurate to 0.1 mg) of ERM-ED103 sample into a nickel crucible, add 3 g of NaOH solid, cover with a lid slightly open, put into a muffle furnace, heat to 700°C, melt for 10 min, cool, leach the melt into a 250 mL beaker with hot water, pipette 50 mL of the above leaching solution into a 250 mL beaker, add calcium carbonate in portions and stir continuously until no bubbles are generated, boil on an electric furnace for 3 min, cool slightly and filter, wash the flask 5 times with hot water, wash the precipitate 10 times, collect the filtrate in a 500 mL conical flask, add 1 drop of (1+1) hydrochloric acid and 1 drop of methyl red, boil for 5 min, cool with running water and transfer to a three-necked flask, titrate with 0.1 mol / L NaOH solution until the color changes from slightly red to yellow (ignoring the volume), add 5 g of mannitol, and add a rotor.

[0063] Step 2: Calibrate the acidometer using the pH standard solution. Titrate the reaction solution diluted 50 times with 0.1 mol / L NaOH standard solution. The pH sampling time interval is 25 s. The titration curve uses the titration volume as the horizontal axis and the pH value as the vertical axis.

[0064] Step 3: After collecting 19 sets of data using the acidometer, use EXCEL software to draw a titration curve. Use EXCEL fitting software to fit the data into a straight line y1=0.0038x+4.8029.

[0065] Step 4: Find the intersection of the straight line and the titration curve through the picture. Here the straight line will have 3 intersections with the titration curve. Select the middle intersection, connect the points on both sides of the middle intersection and extend it to get another straight line, y2 = 0.0076x + 1.612, y1 and y2 intersect at one point (840, 8.00), that is, the titration endpoint volume is 840μL, and the titration endpoint pH is 8.00.

[0066] Step 5: According to formula (3), after deducting the volume consumed by the blank sample of 30 μL, the total boron content in the corresponding boron nitride is 43.3%.

[0067] Example 3 :

[0068] This embodiment provides a method for determining the free boron content in boron carbide, comprising the following steps:

[0069] Step 1: Weigh 0.5 g (accurate to 0.1 mg) of ERM-ED102 sample, add 15 mL of hydrogen peroxide, 10 drops of nitric acid, connect a condenser, slowly heat to a slight boil, reflux for 40 minutes, and remove it after the free boron is completely decomposed. Wash the condenser 3 times with cold water, add calcium carbonate in portions and stir continuously until no bubbles are generated, boil on an electric stove for 3 minutes, cool slightly and filter, wash the flask 4 times with hot water, wash the precipitate 10 times, collect the filtrate in a 500 mL conical flask, add 1 drop of (1+1) hydrochloric acid and 1 drop of methyl red, boil for 5 minutes, cool with running water, transfer to a three-necked flask, titrate with 0.1 mol / L NaOH solution until the color changes from slightly red to yellow (ignoring the volume), add 5 g of mannitol, and add a rotor.

[0070] Step 2: Use pH standard solution to calibrate the acidity meter, titrate the test solution with 0.1 mol / L NaOH standard solution, sample pH time interval is 30s, and the titration curve uses titration volume as the horizontal axis and pH value as the vertical axis.

[0071] Step 3: After collecting 19 sets of data using the acidometer, use EXCEL software to draw a titration curve. Use EXCEL fitting software to fit the data into a straight line y1=0.0035x+5.0111.

[0072] Step 4: Find the intersection of the straight line and the titration curve through the picture. Here the straight line will have 3 intersections with the titration curve. Select the middle intersection, connect the points on both sides of the middle intersection and extend it to get another straight line, y2 = 0.0065x + 3.02, y1 and y2 intersect at one point (664, 7.34), that is, the titration endpoint volume is 664μL, and the titration endpoint pH is 7.34.

[0073] Step 5: According to formula (2), after deducting the blank sample volume of 24 μL and the boron oxide content, the free boron content in the corresponding boron carbide is 0.118%.

[0074] Example 4 :

[0075] The difference from Example 1 is that the pH sampling time is 22s (one drop is added every 22 seconds and the test is performed immediately after the addition), and the other parameter settings and the specific preparation process are the same as those in Example 1.

[0076] Example 5 :

[0077] The difference from Example 1 is that the pH sampling time is 27 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0078] Example 6:

[0079] The difference from Example 2 is that the pH sampling time is 20 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0080] Example 7 :

[0081] The difference from Example 2 is that the pH sampling time is 40 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0082] Example 8 :

[0083] The difference from Example 3 is that the pH sampling time is 20 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0084] Example 9 :

[0085] The difference from Example 3 is that the pH sampling time is 37 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0086] Example 10 :

[0087] The difference from Example 1 is that the concentration of NaOH is 0.01 mol / L, the pH sampling time is 22 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0088] Embodiment 11 :

[0089] The difference from Example 1 is that the concentration of NaOH is 0.01 mol / L, the pH sampling time is 27 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0090] Example 12 :

[0091] The difference from Example 1 is that the concentration of NaOH is 0.01 mol / L, the pH sampling time is 30 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0092] Embodiment 13 :

[0093] The difference from Example 1 is that the concentration of NaOH is 0.15 mol / L, the pH sampling time is 22 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0094] Embodiment 14 :

[0095] The difference from Example 1 is that the concentration of NaOH is 0.15 mol / L, the pH sampling time is 27 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0096] Embodiment 15 :

[0097] The difference from Example 1 is that the concentration of NaOH is 0.15 mol / L, the pH sampling time is 30 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0098] Example 16 :

[0099] The difference from Example 2 is that the concentration of NaOH is 0.05 mol / L, the pH sampling time is 20 s, and the other parameter settings and specific preparation process are the same as those in Example 1.

[0100] Embodiment 17 :

[0101] The difference from Example 2 is that the concentration of NaOH is 0.05 mol / L, the pH sampling time is 25 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0102] Embodiment 18 :

[0103] The difference from Example 2 is that the concentration of NaOH is 0.05 mol / L, the pH sampling time is 40 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0104] Embodiment 19 :

[0105] The difference from Example 2 is that the concentration of NaOH is 0.2 mol / L, the pH sampling time is 20 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0106] Embodiment 20 :

[0107] The difference from Example 2 is that the concentration of NaOH is 0.2 mol / L, the pH sampling time is 25 s, and the other parameter settings and specific preparation process are the same as those in Example 1.

[0108] Embodiment 21 :

[0109] The difference from Example 2 is that the concentration of NaOH is 0.2 mol / L, the pH sampling time is 40 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0110] Embodiment 22 :

[0111] The difference from Example 3 is that the concentration of NaOH is 0.05 mol / L, the pH sampling time is 20 s, and the other parameter settings and specific preparation process are the same as those in Example 1.

[0112] Embodiment 23 :

[0113] The difference from Example 3 is that the concentration of NaOH is 0.05 mol / L, the pH sampling time is 30 s, and the other parameter settings and specific preparation process are the same as those in Example 1.

[0114] Embodiment 24 :

[0115] The difference from Example 3 is that the concentration of NaOH is 0.05 mol / L, the pH sampling time is 37 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0116] Embodiment 25 :

[0117] The difference from Example 3 is that the concentration of NaOH is 0.15 mol / L, the pH sampling time is 20 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0118] Embodiment 26 :

[0119] The difference from Example 3 is that the concentration of NaOH is 0.15 mol / L, the pH sampling time is 30 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0120] Embodiment 27 :

[0121] The difference from Example 3 is that the concentration of NaOH is 0.15 mol / L, the pH sampling time is 37 s, and other parameter settings and specific preparation process are the same as those in Example 1.

[0122] Test Example 1 :

[0123] This test example conducted precision experimental tests on Examples 1 to 3, as shown in Table 1.

[0124] Precision refers to the degree to which the results of repeated measurements under the same conditions are consistent with each other. The size of the precision is expressed by the relative standard deviation. The smaller the deviation, the higher the precision.

[0125] Table 1

[0126]

[0127] Test Example 2 :

[0128] This test example tests and compares the boron oxide content in boron carbide in nine groups of experiments in Examples 1, 4-5, 10-15, as shown in Table 2:

[0129] Table 2

[0130] project Test value average value RSD% Boron Oxide Content in Boron Nitride 0.069,0.064,0.069,0.065,0.066,0.066,0.069,0.068,0.068 0.067 2.6

[0131] This test example tests and compares the total boron content in boron carbide in nine groups of experiments in Examples 2, 6-7, 16-21, as shown in Table 3:

[0132] Table 3

[0133] project Test value average value RSD% Total Boron in Boron Nitride 43.3,43.1,43.1,43.5,43.6,43.7,43.2,43.1,43.5 43.3 0.6

[0134] This test example tests and compares the free boron content in boron carbide in nine groups of experiments of Examples 3, 8-9, 22-27, as shown in Table 4:

[0135] Table 4

[0136] project Test value average value RSD% Free Boron in Boron Carbide 0.114,0.112,0.111,0.116,0.117,0.113,0.115,0.116,0.111 0.115 1.3

[0137] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for determining the boron content in a boride, characterized in that: The steps include: S1. Pretreating the boron-containing compound to obtain a solution to be titrated; S2, titrating the solution to be titrated with an alkaline titration solution, and measuring the pH value of the solution to be titrated and the volume of the alkaline titration solution in real time during the titration process; S3, drawing a titration curve and fitting a first straight line; S4, connecting the points on both sides of the intersection of the first straight line and the titration curve and extending them to obtain a second straight line; S5. The volume corresponding to the intersection of the first straight line and the second straight line is the titration endpoint volume. Based on the obtained titration endpoint volume, the boron content in the boride is calculated.

2. The measuring method according to claim 1, characterized in that In step S1, the pretreatment is to digest the boron-containing compounds.

3. The measuring method according to claim 1, characterized in that In step S2, the alkaline titration solution is selected from one of sodium hydroxide and potassium hydroxide.

4. The assay method according to claim 3, wherein The concentration of the titration solution is 0.01 mol / L to 0.2 mol / L.

5. The measuring method according to claim 1, characterized in that In step S2, the pH value of the solution to be titrated is measured using an MP230 acidity meter from Mettler Toledo. The acidity meter needs to be calibrated before use to determine the concentration of the titration solution for titration, and the pH corresponding to the titration volume is recorded with the acidity meter.

6. The measuring method according to claim 1, characterized in that In step S2, the pH value of the solution to be titrated is measured once every 20s to 40s.

7. The measuring method according to claim 1, characterized in that In step S2, the solution to be titrated is magnetically stirred during the titration process, and the stirring speed is 50-200 rpm.

8. The assay method according to claim 1, wherein In step S3, the titration curve is drawn using EXCEL software, and the first straight line is fitted using EXCEL software; further preferably, the titration curve takes the volume of the alkaline titration solution as the abscissa and the pH value of the solution to be titrated as the ordinate; preferably, in step S3, the first straight line is y1=ax+b; In step S4, the second straight line is fitted using EXCEL software; the second straight line is y2=cx+d.

9. The measuring method according to claim 1, characterized in that In step S5, the first straight line and the titration curve have three intersection points.

10. The measuring method according to claim 1, characterized in that In step S5, the boron content in the boride is calculated according to the following formulas (1), (2), (3): Where: B2O3 is the boron oxide content; B 游离 is the free boron content; B 总 is the total boron content; C is the concentration of NaOH standard solution, in mol / L; V0 is the volume of NaOH consumed by the blank, in mL; V is the volume of NaOH consumed by the sample, in mL; m is the mass of the sample, in g.

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