|Acid dissolve rate
Solid. Generates negative pressure and heats up by sucking particles.
Vacuum generates constant negative pressure on any space it occupies, meaning you can use flood fill to vacuum whole areas out.
Vacuum acts like Void otherwise, and absorbs any particles that are moving into it (but NOT particles that are simply touching it. It's possible to line vacuum with other elements provided they don't move into it.)
Make special note that Vacuum gains heat whenever it consumes anything.
Can be destroyed by BOMB.