He will be available as long as you helped him in the "Forefathers' Eve" quest.
Alchemists
Locations on Velen / Novigrad
1
Alchemist
Show the map
2Pellar
3Priest of Eternal Fire
Related quests: Free Spirit
Show the mapLocations on The Skellige Isles
4Freya Priestess
Show the map
5Gremist
Complete the "Practicum in Advanced Alchemy" quest for him.
6Jonna
Related quests: The Nithing
Show the map