GB/T 15072.5-1994 Chemical analysis methods for precious metals and their alloys - Determination of silver content in gold and palladium alloys
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Chemical analysis methods for precious metals and their alloys
Determination of silver content in gold and palladium alloys
Gotd.Palladium alloys - Determination of silver content1 Subject content and scope of application
This standard specifies the method for determining the silver content in gold and palladium alloys. GB/T 15072.5-- 94
This standard is applicable to AuAgPr25-6.0, AaAgCu35-5.0, AnAgCu20-30, AuAntuil3.0-0.AuAgCuMnGd33.5-3.0-2.6-0.4, PdAgCuAuPtZn30-14 10-10.1.0, PdAgCu32-28. Determination of silver content in PrtAgCu54-31PdAgCu58-32, PdAgCu65-20, PdAgCu68-27, PdAg40, PdAg8o alloys Determination model: 15, 90%.
2 Reference standards
GB1.4 Standardization work guidelines Chemical analysis method standard drafting regulations GB1467 General principles and regulations for chemical analysis methods of metallurgical products 3 Method summary
Gold alloy, palladium silver copper gold platinum zinc alloy sample is dissolved with mixed acid. Palladium silver copper alloy, palladium silver alloy sample is dissolved in ammonia medium with sodium iodide, silver-silver iodide electrode is used as indicator electrode, saturated calomel electrode is used as reference electrode, potassium iodide standard is used to titrate to reduce the silver (1), and the end point is indicated by potentiometric method.
4 Reagents
4.1 Hydrochloric acid (pl.19g/ml).
4.2 Nitric acid (ol.42g/ml), high-grade pure. 4.3 Ammonia water (1→-1).
4.4 Silver standard solution: Weigh 3.0000g metallic silver (99.99%) in a 250ml beaker. Add 40ml nitric acid (1+1, high-grade pure: Heat until completely dissolved, drive out all nitrogen oxides, remove, cool to room temperature, transfer to a 1000mL volumetric flask. Dilute to a constant concentration with deionized water and mix well. This solution contains 3mg silver in 1mL. Store away from light. 4.5 Potassium iodide standard titration solution: Lc (KI) = C.020mol/1. 4.5.1 Preparation: Weigh 9.96g potassium iodide, dissolve in water. Dilute to 3000mL, mix. 4.5.2 Calibration: Calibration is parallel to the determination of the sample. Carry out. Take two portions of 15.00ml silver standard solution and place them in 100ml beakers respectively, add 9ml ammonia water, use silver-silver iodide electrode as the reference electrode: saturated argon electrode as the reference electrode, use potassium iodide standard titration solution to titrate to the endpoint determined by electron microscope, the endpoint substitution method is shown in Appendix A (reference). The range of the volume of potassium iodide standard titration solution consumed in parallel calibration should not exceed (.101, take its half mean.
Calculate the actual concentration of potassium iodide standard titration solution according to formula (1): Approved by the State Administration of Technical Supervision on May 11, 1994 and implemented on December 1, 1994
GB/T 15072. 5-94
V. X 0. 107 87
Wherein: c----actual concentration of potassium iodide standard titration solution, mol/L; mg
-mass of silver removed from silver standard solution, g; V. —volume of potassium iodide standard titration solution consumed in calibration, ml.; 0. 107 87--
5 Apparatus
The mass of silver in grams equivalent to 1.00mL. potassium iodide standard titration solution (c(KI)-1.000mol/L]. 5.1 Potentiometric titration apparatus
5.1.1 Potentiometer: accuracy 1mV;
5.1.2 Indicator electrode: silver-silver iodide electrode (see Appendix B for preparation method); 5.1.3 Reference electrode: saturated calomel electrode. 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
Silver content.%
15.00~～25.00
>25. 00~ 30. 00
>30. 00~70. 00
>70. 00~90. 00
Carry out two independent determinations and take the average value. 7.2 Determination
7.2.1 Dissolution
Sample quantity g
7.2.1.1 Place the palladium-silver alloy sample in a 100mL beaker, add 5mL nitric acid, cover with surface III, heat at low temperature until the sample is completely dissolved, evaporate to a moist state, and cool. Wash the surface blood and the wall of the beaker with water, add 9mL ammonia water and 20mL water. The following is carried out according to 7.2.3. 7.2.1.2 Place the silver-copper alloy sample in a 100mL beaker, add 5mL nitric acid, cover with surface III, heat at low temperature until the sample is completely dissolved, evaporate to a moist state, and cool. Wash the surface III and the cup wall with water, add 5mL hydrochloric acid, cover the surface III, evaporate at low temperature to about 0.5mL. Cool, and wash the surface dish and the cup wall with water.
7.2.1.3 Place the gold alloy or palladium-silver-copper-gold-platinum-zinc alloy sample in a 100mL beaker, add 40ml. hydrochloric acid and 7mL nitric acid, cover the surface dish, heat at low temperature until the sample is completely dissolved, evaporate to about 0.5ml., and cool. Wash the surface blood and the cup wall with water. 7.2.2 Treatment of residues
7.2.2.1 Add 40ml. of water to the residue (7.2.1.2) or (7.2.1.3), boil until clear, remove, and cool to room temperature away from light. 7.2.2.2 Use medium-speed filter paper to decant the upper clear liquid, and wash the precipitate and filter paper in the beaker with water three times each. 7.2.2.3 Dissolve the precipitate on the filter paper into the original beaker with 8 ml of ammonia water in batches, and wash the filter paper three times with water. Shake the beaker, and after the precipitate is dissolved, add 20 ml of water along the wall of the beaker.
7.2.3 Titration
GB/T 15072.5-94
Insert a silver-silver iodide indicator electrode and a saturated calomel reference electrode into the test solution (7.2.1.1 or 7.2.2.3), start the electromagnetic stirrer, and titrate with potassium iodide standard titration solution to the determined endpoint potential. 8 Expression of analysis results
Calculate the percentage of silver according to formula (2):
Ag(%) = #×V × 0. 107 87 × 100mol
The actual concentration of potassium iodide standard titration solution, mol/L; Where: c—
V, the volume of potassium iodide standard titration solution consumed by the titration test solution, mL; the mass of the sample, g;
0.10787—the mass of silver in grams equivalent to 1.00mL potassium iodide standard titration solution Cc (KI) 1.000mol/L). The result should be expressed to two decimal places.
9 Allowable difference
The difference in analysis results between laboratories should not be greater than the allowable difference listed in Table 2Table 2
Silver content
15. 00~25. 00
>25. 00~35. 00
>35. 00~80. 00
>80.00~90.00
Allowable difference
GB/T 15072.5-94
Appendix A
Method for determining endpoint potential
(Reference)
Pipette 15.00mL of silver standard solution into a 100ml beaker, add 9mL of ammonia water and 10mL of water, insert a silver-silver iodide indicator electrode and a saturated calomel reference electrode, start an electromagnetic stirrer, and titrate with potassium iodide standard titration solution. At the beginning of titration, potassium iodide standard titration solution can be added quickly. Each time 5.0ml is added, the potential (E) is recorded. When approaching the end point, it should be added slowly. Each time 0.10ml is added, the potential is recorded. The potential () is used as the ordinate and the volume (V) of potassium iodide standard titration solution added is used as the horizontal axis to draw a graph to obtain the end point potential. Alternatively, the end point potential can be obtained by the method of graded derivatives.
Appendix B
Method for making silver-silver iodide electrode
(reference)
Take a pure silver wire with a diameter of 1mm and a length of about 180mm, polish it with metallographic sandpaper, wind one end into a spiral shape with a diameter of about 5mm for 5 turns, rinse it with water, and immerse it in potassium iodide solution (4.5), with silver wire as anode and platinum wire as cathode, polarize for 2000s with 1mA DC power supply to make silver-silver iodide electrode,
Additional remarks:
This standard is proposed by China Nonferrous Metals Industry Corporation. This standard is drafted by Kunming Precious Metals Research Institute. This standard is drafted by Kunming Precious Metals Research Institute. The main drafters of this standard are Luo Yijiang and Dong Shouan. From the date of implementation of this standard, the former Ministry of Metallurgical Industry standards YB946 (Au-9)--78 "Chemical Analysis Methods for Gold, Silver, Platinum Alloys", YB946 (Au-15)--78 "Chemical Analysis Methods for Gold, Silver, Copper, Manganese, and Vanadium Alloys", and YB946 (Pd-1)-78 "Chemical Analysis Methods for Palladium-Silver Alloys" shall be invalid.
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