Doctor Martin Felben is a Horde Alchemy trainer located in The Apothecarium in Undercity.
He is in the Apothecarium, underground in a human torture chamber. He will be the first NPC you see at the end of the ramp.
You can learn Alchemy here and train up to skill 75. Past 75 go to Doctor Marsh in Undercity.
Undercity
Doctor Martin Felben
