Addition of common explosives/energetics, and possibly a few exotic ones (TNT, TATP, Ammonium Nitrate, nitroglycerine, nitrocellulose, azidoazide azide, octonitrocubane, etc)
Addition of more toxins/psychoactive compounds with various potion effects
Toxic elements and chemicals can be applied to weapons and arrows
Explosive chemicals can be detonated/crafted into explosives in some manner
Flammable chemicals can be burned in some manner
Group 2 elements+ingots explode when thrown into water
Ability to grow crystals of all elements that make sense via a crystallizer (crystals would be their own section in chem lib), though the machine itself might be a better fit for Techemistry
Addition of gemstones such as sapphire, ruby, citrine, aquamarine, etc
Blocks of elements as a part of chem lib
Additions of all common acids
Placeable liquid buckets for all elements and chemicals that make sense (not the minechem feature of clicking with a certain quantity of an element)
Acids, mercury, bromine, and other toxic liquids harm the player when stepped in