Oleum, even if you can buy it, is horribly expensive from any of the known chemical suppliers (over $100 per liter). It can also exist as ice- or fiber-like crystals or as a gas. Sulfur trioxide will dissolve in water to make sulfuric acid.. Preparation of Sulfur Trioxide and Oleum, by GARAGE CHEMIST This is a new preparative pathway to sulfur trioxide, with completely over-the-counter chemicals and without the need for fancy apparatus, like catalyst tubes and such. Water is added to control the sulfuric acid to the desired strength. Discover sulfur trioxide in Alchemy Classic How to make sulfur trioxide in Alchemy Classic What can you make with sulfur trioxide in Alchemy Classic Walkthrough brought in and burned to make sulfur dioxide (SO 2). In the second stage, sulfur dioxide reacts with more oxygen to make sulfur trioxide: \[sulfur~dioxide + oxygen \rightleftharpoons sulfur~trioxide\] Manufacture of Sulfuric Acid - The Contact Process.. How is Sulfur trioxide made into Sulfuric Acid?. The sulfur trioxide is absorbed in sulfuric acid. This is the balanced chemical equation for the reaction of sulfur trioxide with water.. sulfur trioxide + water sulfuric acid SO 3 (g) + H 2 O (l) H 2 SO 4 (aq) The SO 2 goes through a series of gas cooling and heat recovery operations, and then is run through a catalytic converter to make sulfur trioxide (SO 3). Sulfur trioxide (SO3) is generally a colorless liquid. Acids and Alkalis. It can react with water to form sulfuric acid.SO3 is also called sulfuric oxide and sulfuric anhydride. Stage 2 - making sulfur trioxide. When SO3 is exposed to air, it rapidly takes up water and gives off white fumes.