sulfuric acid; chromic acid in water 1.) 20 min, -6 deg C - 0 deg C; 2.) room temp., 3.5 h.;

1: 81 percent / nitric acid (d=1.42), conc. sulphuric acid / 1.) not over 35 deg C; 2.) 30 min, room temp. 2: 53 percent / conc. sulphuric acid, anhydrous chromic acid / H2O / 1.) 20 min, -6 deg C - 0 deg C; 2.) room temp., 3.5 h. View Scheme

sulfuric acid; boron trifluoride; sulfur trioxide; nitric acid T=150°C;