The American Chemical Society provides many of their conference papers to members, but they can be difficult to locate by non-members. They publish both abstracts and preprints that are completely different publications. Prior to each national meeting, many ACS divisions send their members either abstracts or preprints of papers to be presented during their portion of the meeting program. Individual ACS divisions publish a heavily cited series called Preprints of Papers, while the main body of ACS publishes a Book of Abstracts. The Book of Abstracts contains abstracts of papers from all divisions and secretariats as well as from the committees that organize technical programming.
ACS also distributes Abstract Separates, which are abstracts of a single division, printed separately from the Book of Abstracts. Division members in good standing are mailed their preferred Abstract Separates prior to national meetings as a member benefit.
Preprints (for recent years) are available to members on the ACS website. If you have a citation to the ACS Book of Abstracts, you may be able to locate some additional information by looking to see which division sponsored the presentation and tracking down the preprints from that division. Some (but definitely not all) symposia have been organized and published by ACS Books or other commercial publishers. Technical Programming Archive of Past National Meetings (2004-onwards) is available online and is browsable for particular papers.
Preprints of Papers are not the full text of the papers that are intended to be presented – they are usually 2-4 pages in length and consist of a summary, the data, figures, nomenclature, and references. Preprints (for recent years) are available to members on the ACS website. Some (but definitely not all) symposia have been organized and published by ACS Books or other commercial publishers.