I have just reached Level 49 Alchemy and have upgraded my Solvent Proficiency to 7 out of a possible 8. Harvesting alchemy solvents yields me Night Oil & Star Dew - levels CP 100 - 140.
When I go to the crafter's writ board and take alchemy writs, however, it asks for level 6 potions/poisons, requiring Cloud Mist and Tar Black.
The writs are supposed to issued at your level of skill, but Alchemy is out of whack at this tier.