The definitive chemistry encyclopedia is the Kirk-Othmer Encyclopedia of Chemical Technology. You can get copies of entries from NYPL Premium Services and other libraries with science collections.
The American Chemical Society publishes a number of good ACS Publications.
The traditional print indexes for chemistry literature were Chemical Abstracts by the Chemical Abstracts Service (CAS), Handbuch (organic chemistry) by Beilstein and Gmelin (inorganic chemistry).
Online tools for researching chemistry journals include:
- CAS's STN platform, an old-school command search platform, which provides Chemical Abstracts and other useful databases.
- SciFinder, a relatively user friendly system, also by CAS, with coverage back at least a couple hundred years
- Reaxys, originally by Beilstein and now owned by Elsevier
- Proquest Dialog, a user friendly platform offering chemical-related databases including Analytical Abstracts by The Royal Society of Chemistry, Chemical Engineering, the Chemical Safety Newsbase, and the Chemical Business NewsBase. If you need to do research in this area and, like me, don't know much about it, call ProQuest Dialog (800-334-2564) and ask the rep where and how to search.