Arcane Quickener

Arcane Quickener is used to cleanse the cauldrons in Western Plaguelands.

Source
Arcane Quickener is sold by Alchemist Arbington at Chillwind Camp in Western Plaguelands for Alliance and Apothecary Dithers at the Bulwark in Tirisfal Glades for the Horde. You must have completed the Cauldron quest line to purchase this item.