A chemistry set is a workbench that uses chemicals to create anything from other chemicals to medical kits, explosives and other fun stuff. Its instrumental in creating certain components that are otherwise impossible or hard to find through scavenging. You can also make useful drugs such as mortilex or the heart wrenching, pleasurable kind such as crank, crack and speed.
Chemistry is quite a bit harder to grind then crafting because the materials are not as readily available, requiring careful scavenging in certain places. Plus, unless you combine it with other skills such as crafting or medic, it won't be very useful (but this probably doesn't matter as most brainy types will also have decent skills in both medic and craft). Chemistry can be a nice way to gain XP for a brainy character, as even common recipes give a fair amount of XP. Help needed