Alchemist can take Sticky Bombs, an “additive 2” that allows you to cause persistent damage when you hit with a bomb.
You mix in an additive to make your bomb’s contents adhere to the target and continue to deal damage. A creature that takes a direct hit from one of your sticky bombs also takes persistent damage equal to and of the same type as the bomb’s splash damage. If the bomb already deals persistent damage, combine the two amounts.
If your attack roll is a critical hit, is this persistent damage doubled?