A high-chloric acid standard titration solution with low freezing point and a preparation method thereof

Abstract

The application discloses a perchloric acid standard titration solution with a low freezing point and a preparation method thereof, and comprises the following steps: S1, a certain amount of perchloric acid is measured, acetic acid is injected under stirring, and the mixture is uniformly stirred to obtain a mixed solution A; S2, a certain amount of propionic acid is added to the mixed solution A under stirring, and the mixture is uniformly stirred to obtain a mixed solution B; and S3, acetic anhydride is added dropwise to the mixed solution B, the mixture is uniformly stirred, and the volume is fixed with acetic acid after cooling, and the perchloric acid standard titration solution is obtained.

Description

Technical Field

[0001] This invention relates to the field of standard chemical reagent preparation technology, and in particular to a standard titration solution of perchloric acid with a low freezing point and its preparation method. Background Technology

[0002] In the national standard GB / T 601-2016 "Preparation of Standard Titration Solutions for Chemical Reagents", the preparation methods for perchloric acid standard titration solutions are as follows: Method ① (most commonly used): Measure 8.7 mL of perchloric acid and add it to 500 mL of acetic acid (glacial acetic acid) while stirring. Mix well. Add 20 mL of acetic anhydride and stir until the solution is homogeneous. After cooling, dilute with acetic acid (glacial acetic acid) to 1000 mL. Method ② (less commonly used): Measure 8.7 mL of perchloric acid and add it to 950 mL of acetic acid (glacial acetic acid) while stirring. Mix well. Take two 5 mL portions and determine the mass fraction of water using pyridine as the solvent according to GB / T 606. Calculate the amount of acetic anhydride to be added to the perchloric acid solution based on the average value w of the two parallel determinations. Add the calculated amount of acetic anhydride and stir well. After cooling, dilute with acetic acid (glacial acetic acid) to 1000 mL and shake well.

[0003] Perchloric acid standard titration solutions prepared according to national standard methods often exhibit a high freezing point. Below 12°C, the solution begins to crystallize, rendering it unusable at low temperatures (e.g., winter). Heating (which should be avoided) is necessary for reuse, hindering testing and potentially altering the solution's properties, thus significantly impacting results. Since national standards do not consider the influence of actual operating temperatures, and the industry lacks effective methods to address the high freezing point without affecting the solution's properties, there is an urgent need for researchers to develop a method to resolve this issue without compromising properties or significantly increasing costs. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems by providing a perchloric acid standard titration solution with a low freezing point and its preparation method. This invention improves the formulation of the perchloric acid standard titration solution by adding a certain amount of propionic acid. Without affecting the properties of the perchloric acid standard titration solution or subsequent calibration and testing, the overall crystallization freezing point of the standard titration solution is lowered, preventing crystallization and solidification at low temperatures. This solves the problem of room temperature not reaching the standard solution's operating temperature during calibration and testing, and improves the perchloric acid standard titration solution's adaptability to temperature environments.

[0005] The technical solution adopted in this invention is as follows: A method for preparing a standard titration solution of perchloric acid with a low freezing point, comprising the following steps:

[0006] S1. Measure a certain amount of perchloric acid, add acetic acid while stirring, and stir to mix evenly to obtain mixed solution A;

[0007] S2. Under stirring conditions, a certain amount of propionic acid is added to mixed solution A, and the mixture is stirred until homogeneous to obtain mixed solution B.

[0008] S3. Add acetic anhydride dropwise to mixed solution B, stir and mix evenly, and after cooling, dilute to volume with acetic acid to obtain the final solution.

[0009] Further, in step S1, 0.85-0.90% of the total volume of the perchloric acid standard titration solution is measured as perchloric acid, and the amount of acetic acid injected is 45-55% of the total volume of the perchloric acid standard titration solution.

[0010] Furthermore, in step S2, the amount of propionic acid added is 10-15% of the total volume of the perchloric acid standard titration solution. The amount of propionic acid added in this invention should not be too high or too low. If it is too low, the crystallization point of the standard solution will not decrease significantly; if it is too high, the standard solution will easily become colored, affecting subsequent calibration observations. Experimental results show that adding 10-15% of the total volume of the perchloric acid standard titration solution is preferable, as it can significantly lower the crystallization point of the standard solution without causing coloration and affecting the results of subsequent calibration experiments.

[0011] Furthermore, in step S3, the amount of acetic anhydride added is 1.5-2.5% of the total volume of the perchloric acid standard titration solution.

[0012] Further, in step S3, the volume is adjusted to 1000 mL with acetic acid.

[0013] Preferably, the method for preparing a perchloric acid standard titration solution with a low freezing point includes the following steps:

[0014] A. Measure 8.7 mL of perchloric acid, add 500 mL of acetic acid while stirring, and mix thoroughly to obtain mixed solution A;

[0015] B. Add 100-150 mL of propionic acid to mixed solution A under stirring conditions, stir and mix evenly to obtain mixed solution B;

[0016] C. Add 20 mL of acetic anhydride to mixed solution B, stir and mix well. After cooling, dilute with acetic acid to 1000 mL to obtain the final solution.

[0017] Furthermore, the present invention also includes a perchloric acid standard titration solution with a low freezing point, wherein the perchloric acid standard titration solution is prepared by the above preparation method.

[0018] Furthermore, the crystallization point of the perchloric acid standard titration solution is not greater than 0°C.

[0019] Furthermore, the perchloric acid standard titration solution is colorless.

[0020] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are as follows: By improving the formulation of the perchloric acid standard titration solution and adding a certain amount of propionic acid to the standard titration solution, the overall crystallization point of the standard titration solution is lowered without affecting the properties of the perchloric acid standard titration solution and subsequent calibration and detection. This ensures that the perchloric acid standard titration solution will not crystallize and solidify under low temperature conditions, the crystallization point of the standard solution is less than 0℃, and the solution color is colorless. This solves the drawback that occurs when the room temperature cannot reach the operating temperature of the standard solution during calibration and detection operations, and improves the adaptability of the perchloric acid standard titration solution to temperature environments. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0022] Comparative Example

[0023] A standard titration solution for perchloric acid is prepared by the following steps:

[0024] S1. Measure 8.7 mL of perchloric acid, add 500 mL of acetic acid while stirring, and stir to mix evenly to obtain mixed solution A;

[0025] S2. Add 20 mL of acetic anhydride to mixed solution A, stir and mix well. After cooling, dilute with acetic acid to 1000 mL to obtain the final solution.

[0026] Example 1

[0027] A standard titration solution of perchloric acid with a low freezing point is prepared by the following steps:

[0028] A. Measure 8.7 mL of perchloric acid, add 500 mL of acetic acid while stirring, and mix thoroughly to obtain mixed solution A;

[0029] B. Add 50 mL of propionic acid to mixed solution A under stirring conditions, and stir to mix evenly to obtain mixed solution B;

[0030] C. Add 20 mL of acetic anhydride to mixed solution B, stir and mix well. After cooling, dilute with acetic acid to 1000 mL to obtain the final solution.

[0031] Example 2

[0032] A standard titration solution of perchloric acid with a low freezing point is prepared by the following steps:

[0033] A. Measure 8.7 mL of perchloric acid, add 500 mL of acetic acid while stirring, and mix thoroughly to obtain mixed solution A;

[0034] B. Add 100 mL of propionic acid to mixed solution A under stirring conditions, stir and mix evenly to obtain mixed solution B;

[0035] C. Add 20 mL of acetic anhydride to mixed solution B, stir and mix well. After cooling, dilute with acetic acid to 1000 mL to obtain the final solution.

[0036] Example 3

[0037] A standard titration solution of perchloric acid with a low freezing point is prepared by the following steps:

[0038] A. Measure 8.7 mL of perchloric acid, add 500 mL of acetic acid while stirring, and mix thoroughly to obtain mixed solution A;

[0039] B. Add 150 mL of propionic acid to mixed solution A under stirring conditions, stir and mix evenly to obtain mixed solution B;

[0040] C. Add 20 mL of acetic anhydride to mixed solution B, stir and mix well. After cooling, dilute with acetic acid to 1000 mL to obtain the final solution.

[0041] Example 4

[0042] A standard titration solution of perchloric acid with a low freezing point is prepared by the following steps:

[0043] A. Measure 8.7 mL of perchloric acid, add 500 mL of acetic acid while stirring, and mix thoroughly to obtain mixed solution A;

[0044] B. Add 200 mL of propionic acid to mixed solution A under stirring conditions, stir and mix evenly to obtain mixed solution B;

[0045] C. Add 20 mL of acetic anhydride to mixed solution B, stir and mix well. After cooling, dilute with acetic acid to 1000 mL to obtain the final solution.

[0046] Example 5

[0047] A standard titration solution of perchloric acid with a low freezing point is prepared by the following steps:

[0048] A. Measure 8.7 mL of perchloric acid, add 500 mL of acetic acid while stirring, and mix thoroughly to obtain mixed solution A;

[0049] B. Add 250 mL of propionic acid to mixed solution A under stirring conditions, stir and mix evenly to obtain mixed solution B;

[0050] C. Add 20 mL of acetic anhydride to mixed solution B, stir and mix well. After cooling, dilute with acetic acid to 1000 mL to obtain the final solution.

[0051] The performance results of the perchloric acid standard titration solutions obtained in the comparative examples and Examples 1-5 are shown in Table 1:

[0052] Table 1. Performance results of the standard solutions in comparative examples and Examples 1-5

[0053] project Propionic acid volume fraction acetic acid volume fraction Solution color Solution crystallization point Comparative Example 0％ 97.13％ colorless Approximately 12℃ Example 1 5％ 92.13％ colorless Approximately 5℃ Example 2 10％ 87.13％ colorless ＜0℃ Example 3 15％ 82.13％ colorless ＜0℃ Example 4 20％ 77.13％ pale yellow ＜0℃ Example 5 25％ 72.13％ pale yellow ＜0℃

[0054] Table 1 shows that when no propionic acid is added to the perchloric acid standard titration solution, the solution is colorless, with a crystallization point of approximately 12℃, indicating a relatively high freezing point. As the amount of propionic acid added increases, the crystallization point gradually decreases to below 0℃, and the solution color gradually changes from colorless to yellow. Therefore, considering all factors, an addition of 10-15% propionic acid is preferable.

[0055] The perchloric acid standard titration solution prepared by this invention has good stability, and its quality is not significantly affected by long-distance transportation, which has been highly praised by customers. Due to the very low crystallization point of the perchloric acid standard titration solution, the product has obvious advantages, and its sales have grown rapidly, achieving great commercial success.

[0056] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a standard titration solution of perchloric acid with a low freezing point, characterized in that, Includes the following steps: S1. Measure a certain amount of perchloric acid, add acetic acid while stirring, and stir to mix evenly to obtain mixed solution A; S2. Under stirring conditions, a certain amount of propionic acid is added to mixed solution A, and the mixture is stirred until homogeneous to obtain mixed solution B; in step S2, the amount of propionic acid added is 10-15% of the total volume of the perchloric acid standard titration solution; the crystallization point of the perchloric acid standard titration solution is not greater than 0℃; the color of the perchloric acid standard titration solution is colorless; S3. Add acetic anhydride dropwise to mixed solution B, stir and mix evenly, and after cooling, make up to volume with acetic acid to obtain the solution; in step S3, the amount of acetic anhydride added is 1.5-2.5% of the total volume of the perchloric acid standard titration solution.

2. The method for preparing a perchloric acid standard titration solution with a low freezing point as described in claim 1, characterized in that, In step S1, 0.85-0.90% of the total volume of the perchloric acid standard titration solution is measured as perchloric acid, and the volume of acetic acid injected is 45-55% of the total volume of the perchloric acid standard titration solution.

3. The method for preparing a perchloric acid standard titration solution with a low freezing point as described in claim 1, characterized in that, In step S3, the volume is adjusted to 1000 mL with acetic acid.

4. The method for preparing a perchloric acid standard titration solution with a low freezing point as described in claim 1, characterized in that, Includes the following steps: A. Measure 8.7 mL of perchloric acid, add 500 mL of acetic acid while stirring, and mix thoroughly to obtain mixed solution A; B. Add 100-150 mL of propionic acid to mixed solution A under stirring conditions, stir and mix evenly to obtain mixed solution B; C. Add 20 mL of acetic anhydride to mixed solution B, stir and mix well. After cooling, dilute with acetic acid to 1000 mL to obtain the final solution.

5. A standard titration solution of perchloric acid with a low freezing point, characterized in that, The perchloric acid standard titration solution is prepared by the preparation method described in any one of claims 1-4.