Manufacture of Sulfuric Acid - The Contact Process.. How is Sulfur trioxide made into 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. Sulfur trioxide (SO3) is generally a colorless liquid. It can react with water to form sulfuric acid.SO3 is also called sulfuric oxide and sulfuric anhydride. Oleum, even if you can buy it, is horribly expensive from any of the known chemical suppliers (over $100 per liter). Sulfur trioxide will dissolve in water to make sulfuric acid.. When SO3 is exposed to air, it rapidly takes up water and gives off white fumes. Stage 2 - making sulfur trioxide. 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 It can also exist as ice- or fiber-like crystals or as a gas. Water is added to control the sulfuric acid to the desired strength. Acids and Alkalis. 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). The sulfur trioxide is absorbed in sulfuric acid. In the second stage, sulfur dioxide reacts with more oxygen to make sulfur trioxide: \[sulfur~dioxide + oxygen \rightleftharpoons sulfur~trioxide\] brought in and burned to make sulfur dioxide (SO 2). 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)