Attack many metals with liberation of hydrogen, which is inflammable and forms explosive mixture, Oxidizing agent. Appearance Colourless liquid,Sp.Gravity at 30 oC 1.837, Boiling point 44.8 oC. Sulphur Trioxide is widely used as a sulphonating agent in chemical industry. Reaction with moist air produces mist, which has severe irritant effect on eyes, skin & air passage,Store the material in MS tank with vent.