Chemical Abstracts Service Chemical Registry System. 10. Registration of substances from pre-1965 indexes of Chemical Abstracts.

The Chemical Abstracts Service Chemical Registry System, operating since 1965, uniquely identifies chemical substances on the basis of molecular structure. Chemical Abstracts Service is now registering chemical substances cited in indexes to Chemical Abstracts prior to 1965. This effort will result in several hundred thousand additional chemical structures, along with their names, being available for online searching in the Registry File. Both the newly registered substances and those already on file are being linked to their pre-1965 citations in Chemical Abstracts in a new file called CAOLD. In this effort the printed Formula Index entries are converted to computer-readable form by using optical character recognition with the data subsequently processed with existing computer programs.