sulfuric acid; nitric acid 3 h; Ambient temperature;

1: 46.6 percent / K2CO3, CuI, copper bronze / 3 h / 200 °C 2: 85 percent / KMnO4, KOH 3: 90 percent / polyphosphoric acid / 4 h / 180 - 200 °C 4: 81 percent / H2SO4, HNO3 / 3 h / Ambient temperature View Scheme

1: 85 percent / KMnO4, KOH 2: 90 percent / polyphosphoric acid / 4 h / 180 - 200 °C 3: 81 percent / H2SO4, HNO3 / 3 h / Ambient temperature View Scheme

1: 90 percent / polyphosphoric acid / 4 h / 180 - 200 °C 2: 81 percent / H2SO4, HNO3 / 3 h / Ambient temperature View Scheme

1: 46.6 percent / K2CO3, CuI, copper bronze / 3 h / 200 °C 2: 85 percent / KMnO4, KOH 3: 90 percent / polyphosphoric acid / 4 h / 180 - 200 °C 4: 81 percent / H2SO4, HNO3 / 3 h / Ambient temperature View Scheme