This standard specifies the method for determining the copper content in gold. This standard is applicable to the determination of copper content in gold (ore gold, smelting crude gold products and recovered gold, etc.). Determination range: 0.5% to 30%. GB/T 15249.3-1994 Chemical analysis method for gold - Determination of copper content by iodine titration GB/T15249.3-1994 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Chemical analysis method for alloyed gold
Determination of copper content by iodometric method
Crude Gold-Deterintnation of copper content-lodometric method
1 Subject content and scope of application
This standard specifies the method for determining the copper content in alloyed gold. GB/T 15249. 3-94
This standard is applicable to the determination of copper content in alloyed gold (ore gold, refined crude gold products and recovered gold, etc.). Determination range: 0.5% to 30%. 2 Reference standards
GB1.4 Guidelines for standardization work Provisions for the preparation of chemical analysis method standards GB1467 General principles and general provisions for chemical analysis method standards for metallurgical products 3. Principle of the method
Weigh a certain weight of the gold sample to be tested, decompose it with dilute nitric acid and hydrochloric acid, separate silver with silver chloride precipitation, reduce gold ions to monomer gold with sulfite, and after separating gold and silver, add sulfuric acid and sulfur trioxide smoke to drive away nitrogen oxides, adjust the acidity with dilute nitrogen water, and mask iron with ammonium bifluoride. In a slightly acidic solution of pH 3.0-4.0, copper (1) reacts with potassium iodide to release iodine, and then titrate with sodium thiosulfate standard solution using starch as an indicator.
4 Reagents
4.1 Potassium iodide.
4:2 Ammonium bifluoride.
4.3 Potassium thiocyanate.
4.4 Hydrochloric acid (el.19g/mL).
4.5 Nitric acid3, 50~7. 00
>7. 00--15. 00
>15. 00~30, 00
5.2 Determination
Test sample + g
Test subtraction total product, mL
Take the test solution volume, mL
5.2.1 Place the test sample (5.1) in a 250mL beaker, add 20ml water, 5mL nitric acid (4.5), cover with surface blood, heat at low temperature for about 30 minutes, remove, cool slightly, slowly add 20mL hydrochloric acid (4.4), heat at low temperature to completely dissolve the sample. 5.2.2 Evaporate to nearly dryness, remove and cool slightly, wash the surface blood and the wall of the beaker with water, add water to a volume of about 100mL, shake well. Heat and boil to dissolve soluble salts, and remove.
5.2.3 Use a small amount of water to wash the surface blood and the wall of the cup. Under constant stirring, slowly add 15mL of sulfurous acid (4.8) and let it stand in a hot place for 30 minutes. 5.2.4 Wash the surface blood, filter the precipitate with medium-speed quantitative filter paper by decantation, wash it with hot water 4 times, then transfer the precipitate to the filter paper, wash the filter paper and the precipitate with hot water 6 times, then use a dropper to wash it with nitric acid (4.6) 3 times [the total amount of nitric acid (4.6) is about 2mL], and wash it with hot water 3 times.
5.2.5 Shake the filtrate and evaporate it to a solution volume of about 40mL, then add 5ml of sulfuric acid (4.7), shake it well and evaporate it until thick sulfur trioxide smoke emerges, remove it, and cool it down. Wash the wall of the cup with water and evaporate it until the sulfur trioxide smoke disappears, remove it, and cool it down. 5.2.6 Add 14 drops (6 drops if full volume is taken) of sulfuric acid (4.7) to wash the wall of the cup until the volume of the solution is about 30 mL, cover, add blood, heat and boil until the salts are completely dissolved, cool to room temperature, transfer to a volumetric flask according to Table 1 (or titrate the full volume), dilute to scale with water, and mix. 5.2.7 Transfer the solution (5.2.6) according to Table 1 to a 250mL beaker and add [0mL water]. 5.2.8 Use ammonia water (4.9) to adjust until blue copper ammonia complex appears, add about 0.5 g of ammonium fluoride, shake well, add 3 g of potassium iodide, immediately titrate with sodium thiosulfate standard solution until light yellow, add 5 mL of starch solution (4.10), continue titrating until light blue, add 0.5-1 g of potassium thiosulfate (do not add potassium thiothioate if the content is less than 1%), shake vigorously until the blue color deepens, and then titrate until the blue color just disappears, which is the end point (when the interfering element is more than 76
, the end point of the titration solution is yellow).
6 Calculation and expression of analysis results
Calculate the percentage of copper according to the following formula
Wu Zhong: c
GB/T 15249. 3- 94
c. V.+ V. X 0. 063 54bzxZ.net
Cu(%):
Actual concentration of sodium thiosulfate standard titration solution, mnl/LTotal volume of test solution, mL:
V,—volume of test solution taken, mL;
V—…-volume of sodium thiosulfate standard titration solution consumed in titration test solution, mL,,m1
0. 063 54
7 Allowable difference
Mass of sample,:
With 1.00 mL sodium thiosulfate standard titration solution [e(Na2S:0,)=1.000 mo1/L] is equivalent to the mass of copper. The difference in the analysis results between laboratories should not be greater than the allowable difference listed in Table 2. Table 2
0. 50~2. 50
>2.5010.00
2-10. 00~ 20. 00
>20. 00-30. 00
Additional Notes:
This standard was jointly proposed by the People's Bank of China Printing Corporation and the State Gold Administration. This standard was drafted by China Gold and Silver Refinery and Changchun Gold Research Institute. This standard was drafted by Beijing Research Institute of Mining and Metallurgy. The drafter of this standard is Zhou Yihua.
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