Such oxides as sulphur trioxide, nitrogen pentoxide, etc., do not possess acid properties except in combination with water.
sulphur trioxide forms thin needle-shaped crystals, arranged in feathery groups.
Small quantities of sulphur trioxide (SO3) may also be formed in the combustion of sulphur.
sulphur trioxide is a colorless liquid, which solidifies at about 15° and boils at 46°.
sulphur trioxide is formed, and as it issues from the tube it is absorbed in water or dilute sulphuric acid.