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GB/T 20899.1-2019 English PDF (GBT20899.1-2019)

GB/T 20899.1-2019 English PDF (GBT20899.1-2019)

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GB/T 20899.1-2019: Methods for chemical analysis of gold ores -- Part 1: Determination of gold content

This Part of GB/T 20899 specifies the method to determine gold content in gold ores. This Part is applicable to the determination of gold content in gold ores. The determination range of Method 1 is 0.20g/t~150.0g/t.
GB/T 20899.1-2019
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 73.060.99
D 46
Replacing GB/T 20899.1-2007
Methods for chemical analysis of gold ores - Part 1:
Determination of gold content
ISSUED ON: DECEMBER 31, 2019
IMPLEMENTED ON: NOVEMBER 01, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Method 1: Fire assay gravimetric method ... 5
3 Method 2: Fire assay gold concentration - flame atomic absorption spectrometry . 11 4 Method 3: Activated carbon enrichment - flame atomic absorption spectrometry .. 19 5 Method 4: Activated carbon enrichment - iodometric method ... 25
Methods for chemical analysis of gold ores - Part 1:
Determination of gold content
WARNING -- Persons using this Standard shall have practical experience in formal laboratory work. This Standard does not address all safety issues. It is the user's responsibility to take appropriate safety and health measures and to ensure compliance with the conditions stipulated by relevant national regulations. 1 Scope
This Part of GB/T 20899 specifies the method to determine gold content in gold ores. This Part is applicable to the determination of gold content in gold ores. The determination range of Method 1 is 0.20g/t~150.0g/t. The determination range of Method 2 is 0.10g/t~100.0g/t. The determination range of Method 3 is 0.10g/t~100.0g/t. The determination range of Method 4 is 0.30g/t~100.0g/t.
2 Method 1: Fire assay gravimetric method
2.1 Method summary
The test material is batched and melted to obtain lead buttons containing precious metals and brittle slag of appropriate mass. Gold, silver and lead buttons are separated by ash blowing to obtain gold-silver composite particles. After the granules are separated by nitric acid, use the gravimetric method to determine the gold content. 2.2 Reagents and materials
Unless otherwise stated, it shall only use the confirmed analytically-pure reagents AND distilled water or deionized water or equivalent-pure water in the analysis. 2.2.1 Sodium carbonate: technically pure, powdery.
2.2.2 Lead oxide: technically pure, powder. The gold content in lead oxide is less than 0.02g/t.
2.2.3 Borax: technically pure, powdery.
2.2.4 Glass powder: particle size ???0.18mm.
2.2.5 Silica: technically pure, powdery.
2.2.6 Potassium nitrate: technically pure, powdery.
2.2.7 Flour.
2.2.8 Covering agent (2+1): Mix two portions of sodium carbonate and one portion of borax.
2.2.9 Pure silver (wAg???99.99%).
2.2.10 Silver nitrate solution (10g/L): Weigh 5.000g of sterling silver (2.2.9). Place in a 300mL beaker. Add 20mL of nitric acid solution (2.2.13). Heat at a low temperature till it is completely dissolved. Cool to room temperature. Transfer it to a 500mL volumetric flask. Use nitric acid solution (2.2.13) to rinse the beaker. Combine the washing liquid into the volumetric flask. Use water to dilute to the scale. Mix well. 1mL of this solution contains 10mg of silver.
2.2.11 Nitric acid (??=1.42g/mL).
2.2.12 Nitric acid solution (1+7).
2.2.13 Nitric acid solution (1+2).
2.3 Instruments and equipment
2.3.1 Assay crucible: The material is refractory clay. The volume is about 300mL or ensure that the depth of placing the test material does not exceed 3/4 of the depth of the crucible.
2.3.2 Magnesia ashtray: Cement (No. 425), magnesia (???0.18mm) and water are mixed evenly according to the mass ratio (15:85:10). Compress and mold on the ashtray. The volume is not less than 5mL. Reserve after 3 months of drying in the shade. 2.3.3 Colorimetric tube: 25mL.
2.3.4 Balance: The resolution is not more than 0.01g.
2.3.5 Balance: The resolution is not more than 0.001mg.
2.3.6 Electric melting furnace: The maximum heating temperature is not lower than 1200???.
2.3.7 Ash blowing electric furnace: the maximum heating temperature is not lower than 1000???.
2.3.8 Pulverizer.
2.3.9 Cast iron mold.
2.4 Specimen
absorption spectrometry
3.1 Method summary
The test material is batched and melted. Obtain proper mass of lead buttons containing precious metals and brittle slag. Gold, silver and lead buttons are separated by ash blowing to obtain gold-silver composite particles. The composite particles are dissolved by nitric acid and aqua regia. Use a flame atomic absorption spectrometer to determine the gold absorbance value at a wavelength of 242.8nm.
3.2 Reagents and materials
Unless otherwise stated, it shall only use the confirmed analytically-pure reagents AND distilled water or deionized water or equivalent-pure water in the analysis. 3.2.1 Sodium carbonate: technically pure, powdery.
3.2.2 Lead oxide: technically pure, powdery. The gold content in lead oxide is less than 0.02g/t.
3.2.3 Borax: technically pure, powdery.
3.2.4 Glass powder: particle size ???0.18mm.
3.2.5 Silica: technically pure, powdery.
3.2.6 Potassium nitrate: technically pure, powdery.
3.2.7 Flour.
3.2.8 Covering agent (2+1): mix two portions of sodium carbonate and one portion of borax.
3.2.9 Pure silver (wAg???99.99%).
3.2.10 Gold (wAu???99.99%).
3.2.11 Silver nitrate solution (10g/L): Weigh 5.000g of sterling silver (3.2.9). Place in a 300mL beaker. Add 20mL of nitric acid solution (3.2.14). Heat at a low temperature till it is completely dissolved. Cool to room temperature. Transfer it into a 500mL volumetric flask. Use nitric acid solution (3.2.14) to rinse the beaker. Combine the washing liquid into the volumetric flask. Use water to dilute till the scale. Mix well. 1mL of this solution contains 10mg of silver.
3.2.12 Nitric acid (??=1.42g/mL).
3.2.13 Hydrochloric acid (??=1.19g/mL).
3.2.14 Nitric acid solution (1+2).
3.2.15 Aqua regia: Mix three volumes of hydrochloric acid and one volume of nitric acid. Prepare when required.
3.2.16 Sodium chloride solution (200g/L).
3.2.17 Hydrochloric acid solution (1+19).
3.2.18 Gold standard storage solution: Weigh 0.5000g of gold (3.2.10). Place in a 100mL beaker. Add 20mL of aqua regia (3.2.15). Heat at a low temperature till it is completely dissolved. Remove and cool to room temperature. Transfer it into a 500mL volumetric flask. Use 20mL of aqua regia (3.2.15) to rinse the beaker. Then use water to wash the beaker. Combine them in the volumetric flask. Use water to dilute to the scale. Mix well. 1mL of this solution contains 1.00mg of gold.
3.2.19 Gold standard solution: Pipette 50.00mL of gold standard stock solution (3.2.18) into a 500mL volumetric flask. Add 10mL of aqua regia (3.2.15). Use water to dilute to the scale. Mix well. 1mL of this solution contains 100??g of gold.
3.3 Instruments and equipment
3.3.1 Test gold crucible: The material is refractory clay. The volume is about 300mL or ensure that the depth of placing the sample does not exceed 3/4 of the depth of the crucible.
3.3.2 Magnesia ashtray: Cement (No. 425), magnesia (< 0.18mm) and water are mixed evenly according to the mass ratio (15:85:10). Compress and mold on the ashtray. The volume is not less than 5mL. It shall be used after drying in the shade for 3 months. 3.3.3 Balance: The resolution is not more than 0.01g.
3.3.4 Electric melting furnace: The maximum heating temperature is not lower than 1200???.
3.3.5 Ash blowing electric furnace: The maximum heating temperature is not lower than 1000???.
3.3.6 Flame atomic absorption spectrometer, equipped with gold hollow cathode lamp. Under the best working conditions of the flame atomic absorption spectrometer, anyone who can achieve the following indicators can be used.
Sensitivity: In a solution consistent with the matrix of the measured test material solution, the characteristic concentration of gold shall not be greater than 0.23??g/mL. Precision: Use the highest concentration standard solution to measure the absorbance 11 times. The standard deviation shall not exceed 1.5% of the mean absorbance. Use 4.2.2 Hydrochloric acid (??=1.19g/mL).
4.2.3 Aqua regia: Mix three volumes of hydrochloric acid (4.2.2) with one volume of nitric acid (4.2.1). Prepare when required.
4.2.4 Aqua regia (1+l): Mix three volumes of hydrochloric acid (4.2.2), one volume of nitric acid (4.2.1) and four volumes of water. Prepare when required.
4.2.5 Hydrochloric acid solution (5+95).
4.2.6 Ammonium bifluoride solution (20g/L).
4.2.7 Sodium chloride solution (200g/L).
4.2.8 Gelatin solution (50g/L).
4.2.9 Activated carbon: The particle size is not greater than 0.074mm. Soak analytically or chemically pure activated carbon in ammonium bifluoride solution (4.2.6) for 3d. Conduct suction-filtration. Use hydrochloric acid (4.2.5) and water to wash 3 times respectively.
4.2.10 Qualitative filter paper.
4.2.11 Activated carbon-pulp mixture: The mass ratio of activated carbon (4.2.9) to qualitative filter paper (4.2.10) is 1:2. Put into a 2L plastic beaker. Crush and mix well. Use hydrochloric acid (4.2.5) and water to wash 3 times respectively.
4.2.12 Gold standard storage solution (1.00mg/mL): Weigh 0.5000g of gold (wAu???99.99%). Place in a 100mL beaker. Add 20mL of aqua regia (4.2.3). Heat at a low temperature till it is completely dissolved. Remove and cool to room temperature. Transfer it into a 500mL volumetric flask. Use water to dilute to the scale. Mix well. 1mL of this solution contains 1.00mg of gold.
4.2.13 Gold standard solution (100??g/mL): Pipette 50.00mL of gold standard stock solution (4.2.12) into a 500mL volumetric flask. Add 10mL of aqua regia (4.2.3). Use water to dilute to the scale. Mix well. 1mL of this solution contains 100??g of gold. 4.3 Instruments and equipment
4.3.1 Activated carbon adsorption suction-filtration device
Insert the glass adsorption column into the hole of the suction filter cartridge. Put a perforated plastic plate inside the column. Insert a piece of filter paper the same size as the diameter of the perforated plastic plate. Pour into pulp. Conduct suction-filtration. After filtering, the pulp layer thickness is about 3mm~4mm. Add activated carbon-pulp mixture (4.2.11). After draining, the thickness is 5mm~10mm. Use water to rinse the column wall. Add a thin layer of pulp. Install the Buchner funnel. Put two pieces of qualitative filter paper on the funnel. Add a little pulp to the edge of the filter paper. 4.4.1 The particle size of the specimen is not more than 0.074mm.
4.4.2 The specimen shall be dried at 100??? ~ 105??? for 1h, and then cooled to room temperature in a desiccator.
4.5 Test steps
4.5.1 Test material
Weigh the specimen according to Table 6, to the nearest of 0.01g.
Conduct two determinations independently. Take the average value as the result. 4.5.2 Blank test
Conduct the blank test with test material.
4.5.3 Determination
4.5.3.1 Place the test material (4.5.1) in the square porcelain boat. Put into the muffle furnace. Heat up to 300 ???, 400 ???, 500 ??? through program. Keep the temperature for 20min, respectively. Then heat up to 650??C. Keep the temperature for 30min~60min. Take out to cool.
4.5.3.2 Transfer the test material to a 400mL beaker. Use water to moisten. Add 100mL of aqua regia (4.2.4). Cover the watch glass. Place it on the hot plate. Heat at a low temperature for 1h. Control the solution volume not less than 50mL. Remove. Add 15mL of gelatin solution (4.2.8). Use water to rinse the watch glass and the beaker wall. Dilute to 100mL. Make the soluble salts dissolved. Stir and cool to 40??C~60??C. 4.5.3.3 Pour the test material solution into the prepared activated carbon adsorption suction-filtration device for suction-filtration. After all the solution in the funnel is filtered dry, use 40??C~60??C hydrochloric acid solution (4.2.5) to wash the beaker 2~3 times. Wash the residue and funnel 4~5 times. Remove the Buchner funnel. Use 40??C~60??C ammonium bifluoride solution (4.2.6) to wash the adsorption column 4~5 times. Use 40??C~60??C hydrochloric acid solution (4.2.5) to wash 4~5 times. Use 40??C~60??C water to wash 4~5 times. Stop pumping after draining.
4.5.3.4 Take out the activated carbon pulp block in the adsorption column. Put into a 50mL porcelain crucible. Dry on an electric stove. Put into a muffle furnace at 700??? for complete ashing. Take out and cool. Add 3 drops of sodium chloride solution (4.2.7), 2mL of aqua regia (4.2.3). Dissolve in a water bath. Steam to nearly dry. Remove and cool. Use hydrochloric acid solution (4.2.5) to leach. Transfer to the corresponding volumetric flask according to Table 6. Use hydrochloric acid solution (4.2.5) to dilute to the scale. Mix well.
- Differences from basic analysis steps;
- Abnormalities observed in the determination;
- Test date.
5 Method 4: Activated carbon enrichment - iodometric
method
5.1 Method summery
After the test material is baked, use aqua regia to dissolve. Gold goes into solution in the form of chloroauric acid. Use activated carbon enrichment gold to separate with the interfering elements. After ashing, use aqua regia to dissolve gold. In hydrochloric acid medium, use potassium iodide to reduce Au3+ to Au+. Release a certain amount of iodine. Use starch as indicator. Use sodium thiosulfate standard solution to titrate. 5.2 Reagents and materials
Unless otherwise stated, it shall only use the confirmed analytically-pure reagents AND distilled water or deionized water or equivalent-pure water in the analysis. 5.2.1 Potassium iodide.
5.2.2 Sodium carbonate.
5.2.3 Hydrochloric acid (??=1.19g/mL).
5.2.4 Nitric acid (??=1.42g/mL).
5.2.5 Glacial acetic acid (??=1.05g/mL)
5.2.6 Aqua regia: Mix three volumes of hydrochloric acid (5.2.3) with one volume of nitric acid (5.2.4). Prepare when required.
5.2.7 Aqua regia (1+1): Mix three volumes of hydrochloric acid (5.2.3) and one volume of nitric acid (5.2.4) with four volumes of water. Prepare when required. 5.2.8 Hydrochloric acid solution (5+95).
5.2.9 Ammonium bifluoride solution (20g/L).
5.2.10 Sodium chloride solution (200g/L).
5.2.11 Acetic acid solution (7+93).
5.2.12 Gelatin solution (50g/L).
5.2.13 Ethylenediaminetetraacetic acid (EDTA) solution (25g/L).
5.2.14 Activated carbon: The particle size is not greater than 0.074mm. Soak analytically or chemically pure activated carbon in ammonium bifluoride solution (5.2.9) for 3d. Conduct suction-filtration. Use hydrochloric acid solution (5.2.8) and water to respectively wash 3 times.
5.2.15 Qualitative filter paper.
5.2.16 Activated carbon-pulp mixture: The mass ratio of activated carbon (5.2.14) to qualitative filter paper (5.2.15) is 1:2. Put into a 2L plastic beaker. Crush and mix well. Use hydrochloric acid solution (5.2.8) and water to respectively wash 3 times. 5.2.17 Gold standard stock solution (100??g/mL): Weigh 0.1000g of gold (wAu???99.99%) into a 50mL beaker. Add 5mL~10mL of aqua regia (5.2.6). Heat at a low temperature till it is completely dissolved. Add 5 drops of sodium chloride solution (5.2.10). Evaporate dry on water bath. After cooling, add 2mL of hydrochloric acid (5.2.3) to repeat evaporation to dry 2~3 times. Add 8mL of hydrochloric acid (5.2.3). After warm heating and dissolving, use water to transfer the solution in the beaker to a 1000mL volumetric flask. Use water to dilute to the scale. Mix well. 1mL of this solution contains 100??g of gold.
5.2.18 Preparation of sodium thiosulfate standard solution:
a) Sodium thiosulfate standard solution ??? [c(Na2S2O3)???0.0003mol/L]: Weigh 2.52g of sodium thiosulfate (Na2S2O3?€?5H2O). Add 0.1g of sodium carbonate (5.2.2). Use the cool water that has been boiled to set the volume constant to 1L (the solution pH is 7.2~7.5). Mix well. Take 30mL of the above solution. Add 0.1g of sodium carbonate (5.2.2). Use the cool distilled water that has been boiled to dilute to 1L. Mix well. Place it for a week. Use after it is calibrated.
b) Sodium thiosulfate standard solution ??? [c(Na2S2O3)???0.0006mol/L]: Weigh 2.52g of sodium thiosulfate (Na2S2O3?€?5H2O). Add 0.1g of sodium carbonate (5.2.2). Use the cool water that has been boiled to set the volume constant to 1L (the solution pH is 7.2~7.5). Mix well. Take 60mL of the above solution. Add 0.1g of sodium carbonate (5.2.2). Use the cool distilled water that has been boiled to dilute to 1L. Mix well. Place it for a week. Use after it is calibrated.
c) Sodium thiosulfate standard solution ??? [c(Na2S2O3)???0.0009mol/L]: Weigh 2.52g of sodium thiosulfate (Na2S2O3?€?5H2O). Add 0.1g of sodium carbonate (5.2.2). Use the cool water that has been boiled to set the volume constant to 1L (the solution pH is 7.2~7.5). Mix well. Take 90mL of the above solution. Add 0.1g of sodium carbonate (5.2.2). Use the cool distilled water that has been boiled to dilute to 1L. Mix well. Place it for a week. Use after it is calibrated.
5.2.19 Sodium thiosulfate standard solution calibration: Pipette the gold standard stock solution (5.2.17) containing 500??g, 1000??g and 1500??g of gold in triplicate.

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