SEARCHING FOR ARTICLES
If you don't already have a specific reference, use one of the index/abstract resources described below that covered the probable date range. This task is easier if you're starting with an author's name. Most chemical papers from this era had only a single author. Knowing the journal makes it easier still. Many journals published their own author and subject indexes annually, and some, such as Liebigs Annalen and Journal of the Chemical Society, helpfully cumulated these indexes every few years to make searching easier. Searching by topic is more difficult. If you're starting with a chemical compound, Beilstein (organic) and Gmelin (inorganic) are the best tools. Subject indexes do exist for some early abstracting sources and individual journals.
Note: 19th century authors often published multiple versions or translations of the same paper in different journals. The Royal Society's Catalogue of Scientific Papers is the best tool for identifying these variants.
CAS has begun selective retro-indexing of pre-1907 literature, starting with:
Various scanned library copies are also available via the Internet Archive.
CAS has added some machine-translated records from the 1897-1906 period to the CAPLUS file. CZ has been digitized by FIZ CHEMIE Berlin for purchase as an intranet database. A structure-searchable database version of CZ is available from InfoChem.
GETTING THE ARTICLE
Once an article is identified, search the Library Catalog and/or WorldCat for holdings of the journal or periodical. Much of this early content still exists only in printed form, although retrospective digitization is progressing in both the open-access and publisher-subscription spheres.
See also the pathfinder on Chemical Biography.