How do I store oxylite?

[僕の名前 (仮)]

it evaporates.

[Rogue]

In liquid. Any item that vaporizes, put it under water, either in a storage container submerged or just a small hole with some water...

[TadaceAce]

It stops evaporating if gas pressure > 2kg in the room. Create a mostly airtight room and vent oxygen into it until it's ~3kg (popped eardrums at 5kg).

Or submerge it, but that either requires it be behind an atmos checkpoint or cause undue stress through sopping wet.

[hats]

Products that sublimate will not do so in high pressure gas or liquid environments. Build a storage compactor in a pool of water and store oxylite, bleach stone, or even polluted dirt inside to keep it from sublimating. You can avoid sopping wet by building a pool exactly the right size for the compactor, filling it with water, and then storing the stuff inside. Dupes will jump over the hole if passing by and will be able to remove stuff from the compactor without going into the water.