Augmented Alchemy( Complete Adventurer)
You can create alchemical items and substances that are much more powerful than normal.
Craft (Alchemy) 24 ranks, INT 21,
Whenever creating an alchemical item or substance (not including poisons), you can choose to make it more powerful than normal by adding 20 to the DC required to create it and multiplying its price by 5.
An augmented alchemical item or substance deals double normal damage (if it deals damage), has twice the normal duration (if it has a duration), adds 2 to the save DC (if it has a save DC), and affects an area twice as wide as normal (if it has an area). If the item or substance doesn't fit any of these categories, then it cannot be affected by this feat.
For example, an augmented flask of alchemist's fire deals 2d6 points of damage (or 2 points of splash damage to all targets within 10 feet) and burns for 2 additional rounds after striking the target (rather than 1). The save DC to extinguish the flames is 17.