Bow-Chemist

The Bow-Chemist specializes in alchemy and potion making. They utilize vial-tipped arrows/bolts to deliver elixers/poisons on impact with varying effects.
(Version 2.0 thanks to u/Anvildude on Reddit for the amazing input!)

Alchemical Expertise

At level 3, the Bow-chemist has developed a way to create vial-tipped arrows. 
(Vial arrows cannot be used in spells. Ex: Conjure Barrage)
You gain access to the Smokepowder, Sleeping Gas, and Light vial-arrow recipes.
You are able to craft a number of Vial arrows equal to your Ranger level per long rest provided you have the required components.

Smokepowder vial arrow: on a hit the target takes 1d6 piercing damage (scales at lvl10) and must make a DC 16 CON save or be choked until your next turn. A choked target has disadvantage on all attack rolls and saving throws.
(requires a pinch of ash and a raven's feather)

Sleeping Gas vial arrow: on a hit the target takes 1d6 piercing damage (scales at lvl10) and must make a DC 16 CON save or fall asleep for 1d4 rounds.
(requires one nightshade pedal and rosewater)

Vial of Light arrow: On a hit the target takes 1d6 piercing damage (scales at lvl10) and is covered in illuminating liquid for 10 rounds.
(requires a small amount of salt and water)

At 5th level, gain access to the Acid vial arrow recipe
Acid vial Arrow: On a hit the target takes 1d6 of piercing damage, plus an additional d8 of Acid damage which repeats for two rounds. (scales at lvl10)
(requires one vial of common acid)

At 7th level gain access to the Noxious Gas vial arrow recipe
Noxious Gas vial Arrow: on a hit the target takes 2d8 poison damage (scales at lvl10) and must make a DC 18 CON save. On a fail the target is poisoned. On a save, the target is not poisoned and takes half damage.
(requires sulfur and phosphorus)

At 9th level gain access to the Firebomb vial arrow recipe
Firebomb vial Arrow: On impact the arrow explodes, all creatures within a 20 foot sphere centered on the impact must make a DC 18 DEX save. On a failed save the target takes 4d10 (scales at lvl12) fire damage. Damage is halved on success.
(requires one vial of alchemist's fire)

Keen shot

At level 3, when you choose to use a vial arrow you can use a bonus action to add your wisdom modifier to the attack roll in addition to other modifiers.

Caustic Resilience

At level 7, due to years of study and experimenting with dangerous chemicals you gain resistance to acid and poison damage.

Without thinking

Starting at level 11, you can use your reaction to make a Vial Arrow attack with advantage at an enemy who makes an attack roll at an ally.

Caustic Immunity

At level 15, choose one of your resistances granted by Caustic Resilience. You are now immune to that damage type.

Caustic Immunity - Acid

Immune to acid damage

Caustic Immunity - Poison

Immune to Poison damage

Double-notch

At level 15, you have learned to fire two arrows with one draw. Both arrows will share the same attack roll.
You may only fire ONE Vial Arrow per shot but can choose different vials for each shot.
(Ex, you can fire a smokebomb and mundane arrow together on one shot, then for your second shot fire a noxious gas and mundane arrow, OR you could just fire 2 mundane arrows each shot.)