Instrument: PolypropyleneDissolving tubeorQuartz digestion tube

Reagent:

1. Nitric acid (HNO3): ρ=1.42g/mL, of superior purity

2. Sulfuric acid (H2SO4): ρ=1.84g/mL, analytical grade

3. Potassium permanganate (KMnO4): 5%

Steps:

1. Take 20mL of sample (or an appropriate amount) into a polypropylene digestion tube.

2. Add 0.5mL of nitric acid HNO3 and 1mL of sulfuric acid H2SO4, and mix the samples evenly.

3. Add 3mL of 5% potassium permanganate KMnO4 solution and let it stand for 15 minutes. If the sample fades from purple or brown, add 2mL of potassium permanganate KMnO4 solution.

4. Place the lid on the digestion tube with a slight gap to allow for some pressure, but do not leave too much smoke.

Heat and reflux at 5.95 ℃ for 2 hours without boiling.

6. After cooling, the sample is completely dissolved.