The Frozen City
Alchemic items and effects are Extraordinary (Ex)
The alchemic arts have come a long way from the brewing of potions and the crafting of parlor tricks like thunder stones. Alchemy now constructs mechanical wonders such as the steam engine the firearm and the Airship. Gasses are well understood as are the basics of chemistry and mechanics. Electricity is just being discovered but no common means of its production has been found.
Alchemic items includes the alchemical items listed pathfinder material as well as firearms and their ammunition. Alchemic items must run on a fuel/energy source and in general follow a real world concept of technology(albeit soft science)
Craft (Alchemy) now covers the creation of the basic alchemical items, thunderstones alchemist fire and the like, firearms ammunition, and more complex alchemic items like steam engines and rail guns. Crafting of Firearms themselves still falls under craft(firearms) but some modifications to the weapons may fall into a bit of both.
Knowledge (Alchemy) covers the science of alchemy and is used both to identify foreign/unknown alchemic inventions as well as to research new ones.
Craft Alchemic Items (Item Creation) is a new feat allowing characters to make items that mimic magical items, spells and other creative items players may research or come across. This includes potions, and the Brew potions feat. The feat requires 5 ranks in Craft (Alchemy).