orthophosphorus acid; water 1.) 3 h, 170 deg C, 2.) 20 min, boiled;

1: With orthophosphorus acid; benzenesulfonic Acid T=65 - 70°C; 0.333333 h; Inert atmosphere; 2: With phosphorus trichoride T=65 - 70°C; 5 h; Inert atmosphere; 3: With hydrogenchloride in water 4 h; RefluxInert atmosphere;

(i) HCl, (ii) aq. HCl; Multistep reaction;

anhydrous phosphorus trichloride in formaldehyd