Turning sulfur dioxide back into acid
Facts checked 1 Nov 2026
Here's where the loop closes. The Sulfur Dioxide from each round of leaching, with a little Oxygen and Deionized Water, becomes Sulfuric Acid again, ready for the next round.
The recipe
The process is called the Wet Sulfuric Acid Process. For every 64 kg of Sulfur Dioxide, 16 kg of Oxygen, and 18 kg of Deionized Water, it makes 98 kg of Sulfuric Acid. It has only one output, so there's no primary output to choose.
One round
- In: About 1,310 tonnes of Sulfur Dioxide, 330 tonnes of Oxygen, and 370 tonnes of Deionized Water.
- Out: About 2,000 tonnes of Sulfuric Acid: everything the last round used.
- Time: About two hours.
Each round of leaching gives back only about 190 tonnes of Oxygen and 230 tonnes of Deionized Water, a little under what this needs. The rest comes from the jobs you ran in Refining: the Oxygen from Making oxygen and carbon monoxide, and the Deionized Water from Water, salts, and calcium.
Run the loop
- Finish a round of leaching.
- On an Academy refinery, click Refine Materials, choose Wet Sulfuric Acid Process, use your crew's warehouse for the inputs and outputs, and turn all the Sulfur Dioxide into acid.
- When it's done, click Finish, and start the next round of leaching with the fresh acid.
- Repeat until all your Weathered Olivine has been leached.
Keep it moving
- About Eight Hours a Round: Leaching and remaking the acid together take about eight and a half hours. Four or five rounds fit into two days, with time to sleep.
- Make Iron as You Go: You don't have to wait for the last round. Once you've some Iron Oxide, you can start making iron, in the next lesson.