in neat (no solvent)
SO3 containing small amount of H2SO4; powdered NaCl; coldness;; distillation; second distillation over molten NaCl (residue Na2S2O7);;
in sulfuryl dichloride
dropwise addition of a SnCl4-containing sulfurylchloride soln. into a SO3-containing sulfurylchloride soln.; formation after boiling for a period of 40 hours; SnCl4:SO3 (molar ratio): 1:6;; removal of sulfurylchloride impurities by washing and drying in a vacuum;;
