Oxygen
From Captain of Industry Wiki
Oxygen is an elemental substance, which is commonly produced by using an Air Separator. Its primary purpose is the infusion into Molten Iron to create Molten Steel in the Oxygen Furnace or, later, the Oxygen Furnace II. Some additional purposes apear later through the game.
Recipes
Below are all the recipes, which contain this item. Note, that some of them may be locked behind Research, and not immediately available in your game.
Production