GB/T 38265.3-2022 Test methods for soft soldering fluxes—Part 3:Determination of acid value—Potentiometric and visual titration methods (English Version)
1 Scope
This document specifies the method for the determination of the acid value of soft brazing agents - potentiometric titration and visual titration, including principles, reagents, apparatus and equipment, test procedures, test data processing, precision, test reports, etc.
This document applies to type 1 and type 2 soft brazing agents as defined in GB/T 15829.
2 Normative reference documents
The contents of the following documents constitute essential provisions of this document through normative references in the text. Among them, note the date of the reference documents, only the date of the corresponding version applies to this document; do not note the date of the reference documents, the latest version (including all the revision of the list) applies to this document.
3 Terminology and definitions
There are no terms and definitions that need to be defined in this document.
4 Principles
4.1 Method A Potentiometric titration
A pre-weighed specimen of soft brazing agent is dissolved in a solvent to form the solution to be measured. A glass electrode is used as the indicating electrode and the solution to be measured is titrated with a standard solution of potassium hydroxide, while the pH or electrode potential (mV) of the solution is recorded. The inflection point is determined from the titration curve between the titration volume of the titrant and the pH or electrode potential (mV) of the solution, and the acid value is calculated.
4.2 Method B Visual titration
A pre-weighed sample of soft brazing agent is dissolved in a solvent to form the solution to be measured and then titrated with a standard solution of potassium hydroxide to calculate the acid value.
5 Reagents
Unless otherwise stated, only reagents confirmed to be analytically pure and distilled or deionised water are used in the analysis.
5.1 Toluene (CH, CH,)
Analytically pure reagents conforming to the requirements of GB/T 684.
5.2 Isopropanol [(CH, )CHOH]
Analytically pure reagent conforming to the requirements of HG/T 2892.
5.3 Ethanol (CH, CH,OH)
Analytically pure reagent conforming to the requirements of GB/T 678.
5.4 Ethyl intoxicating toluene mixture
5.5 Potassium hydroxide ethanol solution (0.1 mol/L)
Use an ethanolic standard solution of potassium hydroxide or a highly concentrated standard solution of potassium hydroxide diluted by ethanol (5.3). Or prepare a 0.1 mol/L ethanolic solution of potassium hydroxide by dissolving 3 g ± 0.1 g of potassium hydroxide in 500 mL of ethanol (5.3); weigh 0.75 g of potassium hydrogen phthalate dissolved in 50 mL of water, add 2 Li of phenolphthalein indicator solution (5.6) and titrate with the prepared ethanolic solution of potassium hydroxide until the solution is pink, use this procedure to calibrate the ethanolic solution of potassium hydroxide.
5.6 Phenolphthalein indicator solution (10 g/L)
Weigh 1 g of phenolphthalein v dissolved in ethanol (95%) and dilute to 100 mL with ethanol (95%).
6 Instrumentation
6.1 Laboratory analytical balance with an accuracy of 0.001 g.
6.2 Millivoltmeter or pH meter.
6.3 Glass electrode.
6.4 Saturated glycerol electrode or silver chloride/silver electrode.
6.5 Adjustable speed magnetic stirrer or mechanical stirrer.
7 Test procedure
7.1 Overview
7.1.1 Dissolve the soft brazing agent specimen in isopropanol (5.2), ethanol (5.3), toluene (5.1) or an ethanol-toluene mixture (5.4). If the solubility is the same, choose isopropanol as the test solvent.
7.1.2 Weigh approximately 1 g of the soft brazing agent to be measured to an accuracy of 0.001 g and record the mass of the soft brazing agent sample m. In the case of liquid soft brazing agents, take measures to prevent evaporation of volatile substances during the measurement.
7.1.3 Transfer the weighed sample into a 250 mL low-profile beaker. Add 100 mL of test solvent (7.1.1) to the beaker, cover with a surface dish and shake lightly until the soft brazing agent is completely dissolved to form the solution to be measured, prohibiting heating during the shaking process and avoiding loss of the soft brazing agent solution.
7.2 Method A Potentiometric titration
7.2.1 Manual method
7.2.1.1 You place the beaker on the burette bear stand with electrodes, stirrer and burette, adjust the stirring speed to full stirring and no splashing.
7.2.1.2 Titrate with potassium hydroxide ethanol solution (5.5), adding to mL per titration. Record the pH or millivoltmeter reading after each titration, adding o.1 mL per titration near the end point, and continue titrating until the excess point is reached.
7.2.1.3 The titration curve is plotted for the potentiometric or pH value and the titrant addition, with the inflection point of the curve corresponding to the end point of the titration. 7.2.1.4 For comparison, a near wrath blank test is performed for all reagents used.
7.2.2 Automatic method
7.2.2.1 The details of the automatic method shall be consistent with the manual titration system.
7.2.2.2 Place the beaker on the base of the burette with the titration equipment installed and adjust the stirring speed until it is fully stirred and free from splashing. Before the titration is started, the parameters for calculating and identifying the specimen should be entered into the evaluation system.
7.2.2.3 The automatic titration system is switched on and the titration curve is plotted automatically.
7.2.2.4 For comparison purposes, a blank test is performed for all reagents used.
7.3 Method B Visual titration
7.3.1 You add 3 drops of phenolphthalein indicator solution (5.6) to the solution to be tested (7.1.3) and titrate with potassium hydroxide ethanol solution (5.5) until the whole solution is light red and lasts for 15 s. Stop the titration.
7.3.2 For comparison, a blank test was carried out for all reagents used.
8 Test data processing
8.1 The acid value AVy (mg/g) was expressed as the mass of potassium hydroxide consumed per gram of non-volatile material (mg), ignoring the base used during the titration.
9 Precision
9.1 Method A Potentiometric titration
Eight inter-laboratory comparative microtests were performed for this method and the repeatability and reproducibility of the results were calculated according to GB/T 6379 (all parts). For five rosin-based soft brazing agents with an acid value (in KOH) of approximately 170 mg/g to 230 mg/g.
The precision is evaluated in Table 1.
9.2 Method B visual titration method
Five inter-laboratory comparison tests were carried out for this method. Repeatability and reproducibility of the results were calculated according to GB/T 6379 (all parts). For 9 rosin-based soft brazing agents with acid values (in KOH) of approximately 160 mg/g to 300 mglg.
The precision is evaluated in Table 2.
10 Test report
The following information should be included in the test report;
a) Identification of the soft brazing agent specimens;
b) the document number and method A or method B;
c) the test results obtained
d) any anomalies during the measurement
e) details of operations not described in this document or other optional operations
f) Date of the test.
1 Scope
2 Normative reference documents
3 Terminology and definitions
4 Principles
5 Reagents
6 Instrumentation
7 Test procedure
8 Test data processing
9 Precision
10 Test report
Standard
GB/T 38265.3-2022 Test methods for soft soldering fluxes—Part 3:Determination of acid value—Potentiometric and visual titration methods (English Version)
Standard No.
GB/T 38265.3-2022
Status
valid
Language
English
File Format
PDF
Word Count
5000 words
Price(USD)
150.0
Implemented on
2022-10-12
Delivery
via email in 1~3 business day
Detail of GB/T 38265.3-2022
Standard No.
GB/T 38265.3-2022
English Name
Test methods for soft soldering fluxes—Part 3:Determination of acid value—Potentiometric and visual titration methods
1 Scope
This document specifies the method for the determination of the acid value of soft brazing agents - potentiometric titration and visual titration, including principles, reagents, apparatus and equipment, test procedures, test data processing, precision, test reports, etc.
This document applies to type 1 and type 2 soft brazing agents as defined in GB/T 15829.
2 Normative reference documents
The contents of the following documents constitute essential provisions of this document through normative references in the text. Among them, note the date of the reference documents, only the date of the corresponding version applies to this document; do not note the date of the reference documents, the latest version (including all the revision of the list) applies to this document.
3 Terminology and definitions
There are no terms and definitions that need to be defined in this document.
4 Principles
4.1 Method A Potentiometric titration
A pre-weighed specimen of soft brazing agent is dissolved in a solvent to form the solution to be measured. A glass electrode is used as the indicating electrode and the solution to be measured is titrated with a standard solution of potassium hydroxide, while the pH or electrode potential (mV) of the solution is recorded. The inflection point is determined from the titration curve between the titration volume of the titrant and the pH or electrode potential (mV) of the solution, and the acid value is calculated.
4.2 Method B Visual titration
A pre-weighed sample of soft brazing agent is dissolved in a solvent to form the solution to be measured and then titrated with a standard solution of potassium hydroxide to calculate the acid value.
5 Reagents
Unless otherwise stated, only reagents confirmed to be analytically pure and distilled or deionised water are used in the analysis.
5.1 Toluene (CH, CH,)
Analytically pure reagents conforming to the requirements of GB/T 684.
5.2 Isopropanol [(CH, )CHOH]
Analytically pure reagent conforming to the requirements of HG/T 2892.
5.3 Ethanol (CH, CH,OH)
Analytically pure reagent conforming to the requirements of GB/T 678.
5.4 Ethyl intoxicating toluene mixture
5.5 Potassium hydroxide ethanol solution (0.1 mol/L)
Use an ethanolic standard solution of potassium hydroxide or a highly concentrated standard solution of potassium hydroxide diluted by ethanol (5.3). Or prepare a 0.1 mol/L ethanolic solution of potassium hydroxide by dissolving 3 g ± 0.1 g of potassium hydroxide in 500 mL of ethanol (5.3); weigh 0.75 g of potassium hydrogen phthalate dissolved in 50 mL of water, add 2 Li of phenolphthalein indicator solution (5.6) and titrate with the prepared ethanolic solution of potassium hydroxide until the solution is pink, use this procedure to calibrate the ethanolic solution of potassium hydroxide.
5.6 Phenolphthalein indicator solution (10 g/L)
Weigh 1 g of phenolphthalein v dissolved in ethanol (95%) and dilute to 100 mL with ethanol (95%).
6 Instrumentation
6.1 Laboratory analytical balance with an accuracy of 0.001 g.
6.2 Millivoltmeter or pH meter.
6.3 Glass electrode.
6.4 Saturated glycerol electrode or silver chloride/silver electrode.
6.5 Adjustable speed magnetic stirrer or mechanical stirrer.
7 Test procedure
7.1 Overview
7.1.1 Dissolve the soft brazing agent specimen in isopropanol (5.2), ethanol (5.3), toluene (5.1) or an ethanol-toluene mixture (5.4). If the solubility is the same, choose isopropanol as the test solvent.
7.1.2 Weigh approximately 1 g of the soft brazing agent to be measured to an accuracy of 0.001 g and record the mass of the soft brazing agent sample m. In the case of liquid soft brazing agents, take measures to prevent evaporation of volatile substances during the measurement.
7.1.3 Transfer the weighed sample into a 250 mL low-profile beaker. Add 100 mL of test solvent (7.1.1) to the beaker, cover with a surface dish and shake lightly until the soft brazing agent is completely dissolved to form the solution to be measured, prohibiting heating during the shaking process and avoiding loss of the soft brazing agent solution.
7.2 Method A Potentiometric titration
7.2.1 Manual method
7.2.1.1 You place the beaker on the burette bear stand with electrodes, stirrer and burette, adjust the stirring speed to full stirring and no splashing.
7.2.1.2 Titrate with potassium hydroxide ethanol solution (5.5), adding to mL per titration. Record the pH or millivoltmeter reading after each titration, adding o.1 mL per titration near the end point, and continue titrating until the excess point is reached.
7.2.1.3 The titration curve is plotted for the potentiometric or pH value and the titrant addition, with the inflection point of the curve corresponding to the end point of the titration. 7.2.1.4 For comparison, a near wrath blank test is performed for all reagents used.
7.2.2 Automatic method
7.2.2.1 The details of the automatic method shall be consistent with the manual titration system.
7.2.2.2 Place the beaker on the base of the burette with the titration equipment installed and adjust the stirring speed until it is fully stirred and free from splashing. Before the titration is started, the parameters for calculating and identifying the specimen should be entered into the evaluation system.
7.2.2.3 The automatic titration system is switched on and the titration curve is plotted automatically.
7.2.2.4 For comparison purposes, a blank test is performed for all reagents used.
7.3 Method B Visual titration
7.3.1 You add 3 drops of phenolphthalein indicator solution (5.6) to the solution to be tested (7.1.3) and titrate with potassium hydroxide ethanol solution (5.5) until the whole solution is light red and lasts for 15 s. Stop the titration.
7.3.2 For comparison, a blank test was carried out for all reagents used.
8 Test data processing
8.1 The acid value AVy (mg/g) was expressed as the mass of potassium hydroxide consumed per gram of non-volatile material (mg), ignoring the base used during the titration.
9 Precision
9.1 Method A Potentiometric titration
Eight inter-laboratory comparative microtests were performed for this method and the repeatability and reproducibility of the results were calculated according to GB/T 6379 (all parts). For five rosin-based soft brazing agents with an acid value (in KOH) of approximately 170 mg/g to 230 mg/g.
The precision is evaluated in Table 1.
9.2 Method B visual titration method
Five inter-laboratory comparison tests were carried out for this method. Repeatability and reproducibility of the results were calculated according to GB/T 6379 (all parts). For 9 rosin-based soft brazing agents with acid values (in KOH) of approximately 160 mg/g to 300 mglg.
The precision is evaluated in Table 2.
10 Test report
The following information should be included in the test report;
a) Identification of the soft brazing agent specimens;
b) the document number and method A or method B;
c) the test results obtained
d) any anomalies during the measurement
e) details of operations not described in this document or other optional operations
f) Date of the test.
Contents of GB/T 38265.3-2022
1 Scope
2 Normative reference documents
3 Terminology and definitions
4 Principles
5 Reagents
6 Instrumentation
7 Test procedure
8 Test data processing
9 Precision
10 Test report
