Attempting to put a vial on a counter another vial is on will pour it into it, however there seems to be no way to put them on the same counter, and the vial isn't emptied in the process.

1. Attempt to put a vial of liquid onto the same counter as a different vial of liquid
2. "You pour the Vial of _ into your Vial of _"
3. The first vial (in inventory) is not emptied, even after relog.

It might be worth mentioning that the other vial may be bugged, since it's still missing the proper sprite. I hadn't intended on mixing the vials at all. I was only reorganizing my stash and forgot that could happen. I don't know if they successfully mixed or not.