1. Instruments and equipment

• 1. Acid reaction device: made of hydrofluoric acid corrosion resistant material.
• 2. Heating and stirring device: can be heated to about 90℃, the speed is adjustable.
• 3. Centrifuge: the maximum speed is not less than 4000 r/min, with a volume of about 400 mL, 50 mL, 10 mL centrifuge tube.
• 4. Electric drying oven: the highest temperature is not less than 20O ℃.
• 5. Refrigerator: Cooling temperature is lower than * 5℃.
• 6. Ultrasonic cleaner or oscillator: output power 250 W.
• 7. High temperature furnace: temperature control 1000℃ 20℃.
• 8. Analytical balance: resolution 0.1mg.
• 9. Agate mortar: diameter about 8 CN.
• 10 crucible: 1000℃ high temperature resistance.
• 11. Sealed laboratory sample preparation mill.
• 12 standard inspection screen: 0.18mm, 0.5mm, 1.0mm.
• 13. Balance: resolution 0.5g, maximum weighing 500g.
• 14 density meter: the relative density measurement range is 1.00 g/mL ~2.50 g/mL.

2. Reagents and Materials

• 1. Hydrochloric acid: chemically pure, with solutions of about Lmol /L,6mol/L and 8mol/L.
• 2. Hydrofluoric acid: chemically pure.
• 3. Glacial acetic acid: chemical pure.
• 4. Arsenic-free zinc particles: pure analysis.
• 5. chloroform: analysis of pure.
• 6. Silver nitrate: analytically pure, prepared into 1% solution.
• 7. Sodium hydroxide: analytically pure, prepared into 0.5mol/L solution.
• 8. Heavy Liquid. The relative density is D ₄²⁰ 2.0g/ml–2.1g/ ml of the relevant solution
• 9. PH paper: pH1–pH12.

3. Separate steps

• 1. Soak in distilled water to remove the supernatant.
• 2. Acid treatment
• 3. The alkali treatment
• 4. Pyrite treatment
• 5. Heavy liquid floated
• 6. Freeze and dry
• 7. Clean soluble organic matter with chloroform
• 8. Determination of burn loss