Anyone with proficiency can use Alchemist's Supplies to craft any of the following items: acid, alchemist's fire, antitoxin, candles, ink, oil, perfume, soap; any kind of process that might require distillation (liqour) or calcination (the creation of oxides) can also be performed with alchemist's supplies. Typical DC to successfully make any of the above is 15. Proficiency checks are made when the alchemist wishes to study a new substance or plant. Typical DCs are between 15 or 20, and it takes one hour. Magical substances that are studied would have a DC of 25 to correctly distill and analyze without spoiling the substance (or blowing up the alchemist).
Anyone with proficiency in this tool can craft poison as per the crafting rules. Any poison listed in the DMG (page 257) can be crafted with a poisoner's kit and the gold piece investment required to craft a poison is half of the market value listed for the poison. Carrion Crawler Mucus, Purple Worm Poison, Serpent Venom, and Wyvern Poison are the only exceptions, these poisons require harvesting from a dead or incapacitated creature. The gold piece value of harvested organs from carrion crawlers, purple worms, poisonous snakes, or wyverns is left to the DM's discretion. When harvesting poison from a creature, a character uses their Proficiency bonus with a Poisoner's Kit but if they are proficient in the Nature skill then their Proficiency bonus is doubled.
Half of the market value must be invested in making an item, one hour per gold piece market value of the item must be spent to make the item, and a minimum of one gold piece must be spent.
Examples: Acid takes 25 hours and costs 12 gold and 5 silver to make, this includes the cost of a vial to put it in; candles take 2 hours to make and 200 of them can be made at a cost of 1 gold; a suit of plate armor takes 1500 hours (94 days minimum) and costs 750 gold.
Time is invested consecutively and the project is ruined if the character is taken away from the project for more than one day.