GB/T 15072.1-1994 Chemical analysis methods for precious metals and their alloys - Determination of gold content in gold and palladium alloys
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National Standard of the People's Republic of China
Chemical analysis methods for precious metals and their alloys
Determination of gold content in gold and palladium alloys
Gold,palladium alloys-Determination of gold content1 Subject content and scope of application
This standard specifies the method for determining the gold content in gold and palladium alloys. GB/T15072.1—94
This standard is applicable to the determination of gold content in the following alloys: AuNi9.0, AuNiCu7.5-1.5, AuNiCr5.0-1.0, AuNi-Cr5.0-2.0, AuNilIn9.0-8.0, AuCuNiZn22.0-2.5-1.0, AuCuNiZnMn18.0-1.8-0.7-0.2, AuNiFeZr 5.0-1.5-0.3、AuNiFeZr9.0-2.0-0.3、AuAgCu20.0-3.0、AuAgCu35.0-5.0、AuAgCuGd35.0-5.0-0.5、AuAgCuMnGd35.5-3.0-2.5-0.5、AuAgPt25.0-6.0.PdAgCuAuPtZn30.0-14.0-10.0-10.0-1.0。Determination range: 5%~95%.
2 Reference standards
GB1.4 Standardization work guidelines Chemical analysis method standard preparation regulations GB1467 General principles and general provisions for chemical analysis method standards for metallurgical products 3 Method summary
The sample is dissolved with mixed acid. In hydrochloric acid-copper sulfate electrolyte solution, gold is titrated with electrogenerated cuprous as titrant, and the potentiometric method indicates the endpoint. The gold content is calculated with the help of physical quantities such as mass, time, current and Faraday constant. 4 Reagents
4.1 Mixed acid: Three unit volumes of hydrochloric acid (p1.19g/mL, high-grade purity) are mixed with one unit volume of nitric acid (p1.42g/mL, high-grade purity). Prepare it when used.
4.2 Mixed acid: Six unit volumes of hydrochloric acid (p1.19g/mL, high-grade purity) are mixed with one unit volume of nitric acid (p1.42g/mL, high-grade purity). Prepare it when used.
4.3 Hydrochloric acid (1+1), high-grade purity.
4.4 Sodium chloride solution (50g/L).
4.5 Cathodic electrolyte solution: weigh 10.0g copper sulfate (CuSO.·5H2O, high-grade pure), place in a 1000mL beaker, add 167mL hydrochloric acid (01.19g/mL, high-grade pure), add water to dissolve and dilute to 1000mL. 4.6 Cathodic electrolyte solution: weigh 10.0g copper sulfate (CuSO, 5H, O, high-grade pure), place in a 1000mL beaker, add 250mL hydrochloric acid (pl.19g/mL, high-grade pure), add water to dissolve and dilute to 1000mL. 4.7 Anodic electrolyte solution: weigh 3.7g potassium chloride and 11.4g cadmium chloride (CdClg·2%H,0), dissolve in 100mL water. 4.8 Nitrogen (≥99.99%).
Approved by the State Administration of Technical Supervision on May 11, 1994 and implemented on December 1, 1994
5 Instruments and devices
GB/T15072.1-94
5.1 Precision coulometric titrator: constant current accuracy is better than or equal to 1/10000; potential detection accuracy is 1mV; six-digit display timing, readable o.1s.
5.2 Electrolytic cell: It consists of a sealed pre-titration cell and a titration cell of similar structure. The schematic diagram of the titration cell is shown below. 5.3 Electromagnetic stirrer.
Schematic diagram of titration cell
1-titration cell beaker, whose ground-mouth beaker cover has an electrode jack, 2-saturated calomel electrode; 3-platinum indicator electrode: ×L, mm, 0.5×20; 4-nitrogen conduit, 5-counter electrode chamber with isolated sand core; 6-metal cadmium anode rod, 7-pin working electrode: area not less than 15cm; 8 stirring rotor
6 Sample
The sample is processed into debris, and finally degreased with acetone, washed, dried and mixed. 7 Analysis steps
7.1 Sample
Weigh the sample according to Table 1, accurate to 0.0001g. Table 1
Gold content, %
5.00~15.00
>15.00~25.00
>25.00~50.00
>50.00~80.00
>80.00~95.00
Carry out two independent measurements and take the average value. 7.2 Determination
7.2.1 Dissolution (group the samples according to the alloys in Table 2) 2
Sample amount + g
AuNiCu7.5-1.5
AuNiCr5.0-1.0
AuNiCr5.0-2.0
AuNiln9.0-8.0
GB/T15072.1—94
Alloy Brand
AuCuNiZn22.0-2.5-1.0wwW.bzxz.Net
AuCuNiZnMn18.0-1.8-0.7-0.02
AuNiFe Zr5.0-1.5-0.3
AuNiFeZr9.0-2.0-0.3
AuAgCu20.0-30.0
AuAgCu35. 0-5. 0
AuAgCuGd35.0-5.0-0.5
AuAgCuMnGd33. 5-5. 0-2. 5-0. 5AuAgPt25.0-6.0
PdAgCuAuPtZn30.0-14.0-10.0-10.0-1.0Total
volume of test solution, mL
Direct determination
Alternate test solution
volume, mL
7.2.1.1 Place the test materials of Groups I and II in Table 2 in a 150mL beaker respectively, add 6mL of mixed acid (4.1), cover the surface with blood, and heat to dissolve.
7.2.1.2 Place the samples of Group V in Table 2 in a 150mL beaker, add 30mL of mixed acid (4.2), cover the surface with blood, and heat to dissolve.
7.2.1.3 Place the samples of Group V directly in the titration cell beaker and dissolve according to 7.2.1.2. 7.2.2 Test solution treatment
After the sample (7.2.1.1 or 7.2.1.2, 7.2.1.3) is dissolved, rinse the surface and the wall of the cup with water, add 1mL of sodium chloride solution, and evaporate to dryness in a boiling water bath. Add 4mL of hydrochloric acid and evaporate to dryness, repeat three times. 7.2.3 Residue treatment
7.2.3.1 For the residue after evaporation of the test solutions of Groups I and I, add 5mL of hydrochloric acid to dissolve, transfer to a 50mL volumetric flask and dilute to the mark with water, mix well, and let stand.
7.2.3.2 For the residue after evaporation of the test solution of group I and group N, add 5mL hydrochloric acid and 10mL water, cover the surface III, heat to boiling, and remove. After cooling, rinse the surface blood, transfer to a 50mL volumetric flask and dilute to the scale with water, mix well, and let it stand. 7.2.3.3 For the residue after evaporation of the test solution of group V, directly place the stirring rotor into the titration cell beaker. 7.2.4 Titration
7.2.4.1 Take about 60mL of cathode electrolyte solution and add it to the pre-titration cell [for the test solution of group I and group N (7.2.3.1, 7.2.3.2), add 4.5 electrolyte solution; for the test solution of group I and group N (7.2.3.1, 7.2.3.2) or the residue of the test solution of group V (7.2.3.3), add 4.6 electrolyte solution], and add 3~4mL of anode electrolyte solution to the electrode chamber. The cathode electrolyte solution is deoxygenated by nitrogen for 8 minutes. Connect the electrodes and the instrument, and electrolyze the blank electrolyte solution with a current of 10 mA to the endpoint potential value of gold (515 ± 5 mV, the determination method is shown in Appendix A), ignoring the titration time.
7.2.4.2 According to Table 2, transfer 1 to N groups of test solutions (7.2.3.1 or 7.2.3.2) to the titration cell beaker respectively, and place the stirring rotor. 7.2.4.3 Add the pre-titrated blank cathode electrolyte solution (7.2.4.1) to the titration cell beaker containing the test solution (7.2.4.2) or the test solution residue (7.2.3.3), cover the ground-mouth beaker with electrodes (as shown in the figure), add the anolyte solution to the electrode chamber, and its liquid level is slightly higher than the catholyte solution level in the beaker, insert the cadmium anode, and continue to pass nitrogen. GB/T15072.1-94
7.2.4.4 Connect the electrodes and the instrument, stir the solution thoroughly, and titrate with a current of 10 mA (for test solutions of groups I to N (7.2.4.2), select an appropriate potential to stop the titration so that the solution eventually reaches a stable gold endpoint potential; for test solution residue of group V (7.2.3.3), stop the titration when the solution potential reaches about 535 mV, wait for 1 min and then titrate again. Repeat this titration operation twice until a stable endpoint potential is reached. Record the titration time.
8 Expression of analysis results
Calculate the percentage of gold according to the following formula:
Ixtxmxv,
Au(%)
nXFXVXm
Where: 1-
Constant current mA:
Titration The time consumed by the gold in the test solution or test solution residue, s; the atomic weight of gold, 196.9665;
the number of electrons transferred, 3;
the Faraday constant, 96484.56;
the total volume of the test solution, mL;
the volume of the test solution taken, mL;
the mass of the sample, mg.
the result should be expressed to two decimal places.
allowable difference
the difference in the analysis results between laboratories should not be greater than the allowable difference listed in Table 3. Table 3
gold content
5.00~15.00
>15.00~50.00
>50.00~95.00
allowable difference
GB/T 15072.1—94
Appendix A
Method for determining the endpoint potential of gold
(reference)
Pipette 2mL of gold standard solution (1mg/mL) into the titration cell beaker, add about 60mL of blank cathode electrolyte solution after deoxygenation, add 3-4mL of anolyte solution to the electrode chamber, connect the electrodes and the instrument, and titrate with a current of 10mA. With potential (E) as the ordinate and time (t) as the abscissa, automatically record the potentiometric titration curve of gold and calculate its endpoint potential. Alternatively, use the second-order derivative method to determine its endpoint potential. Additional notes:
This standard was proposed by China Nonferrous Metals Industry Corporation. This standard was drafted by Kunming Precious Metals Research Institute. This standard was drafted by Kunming Precious Metals Research Institute. The main drafters of this standard are Dong Shouan and Hao Jiangchun. From the date of implementation of this standard, the former Ministry of Metallurgy Standard YB946 (Pd-7) 78 "Chemical Analysis Method for Palladium Silver Gold Nickel Alloy" shall be used as the standard
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