GB/T 20899.3-2019Methods for chemical analysis of gold ores—Part 3:Determination of arsenic content (English PDF)

2.1 Principle

The sample was decomposed by acid, and arsenic was reduced by arsenic-free zinc particles in 1.0 mol/L ~ 1.5 mol/L sulfuric acid medium to generate arsenic gas.

Silver dithiocarbamate (hereinafter referred to as copper reagent silver salt) trichloromethane solution absorption. Silver ions in silver salts of copper reagents reduced by arsenide it becomes red colloidal silver. The absorbance was measured at a wavelength of 530 nm of the spectrophotometer.

2.2 Reagents and materials

Unless otherwise stated, only reagents and distilled or deionized or fairly pure water identified as analytically pure were used in the analysis.

2.2.1 Arsenic-free zinc particles.

2.2.2 Potassium Chlorate.

2.2.3 Trichloromethane.

2.2.4 Nitric acid (rho = 1.42g/mL).

2.2.5 Sulfuric acid solution (1 1).

2.2.6 Tartaric acid solution (400g/L).

2.2.7 Potassium iodide solution (300g/L).

2.2.8 Tin dichloride solution (400g/L). Prepared with hydrochloric acid solution (1 1).

2.2.9 Triethanolamine (or triethylamine) trichloromethane solution (3 97).

2.2.10 Ammonium ferric sulfate solution [rho (Fe) = 20g/L]. Weigh 108g [NH4Fe (SO4) 2 · 2H2O], add water and 10mL sulfuric acid (2.2.5) after stirring and dissolving, transfer to a 1000mL volumetric flask, dilute with water to the mark, and shake well.

2.2.11 Copper reagent silver salt trichloromethane solution (2g/L). Weigh 1g of copper reagent silver salt into a 1000mL reagent bottle, add 500mL three ethanolamine trichloromethane solution (2.2.9), stir to dissolve, stand still overnight, and use after filtering. Store in brown reagent bottle.

2.2.12 Arsenic standard solution (1000µg/mL). Certified standard solution.

2.2.13 Arsenic standard solution I (100 µg/mL). Pipette 10.00 mL of arsenic standard solution (2.2.12) into a 100 mL volumetric flask and add 5 mL nitric acid (2.2.4), diluted with water to the mark, and mixed.

2.2.14 Arsenic standard solution II (5 µg/mL). Transfer 5.00 mL of arsenic standard solution I (2.2.13) into a 100 mL volumetric flask, add 5 mL nitric acid (2.2.4), diluted with water to the mark, and mixed.

2.2.15 Lead acetate absorbent cotton. Soak the absorbent cotton in 100mL lead acetate solution (100g/L, containing 1mL glacial acetic acid), remove, and dry after use.