To search the CAS registry number database, it is necessary to have either the CAS number, the common or trade name, or the chemical name for the substance of interest. As of October 2015, the CAS registry number database is maintained by the Chemical Abstracts Services and contains specific information about approximately 102 million organic and inorganic substances as well as information about over 66 million DNA sequences.
The CAS number is a unique numeric sequence assigned to a particular substance. The numbers can be up to 10 digits long, separated into three parts by hyphens. They are internationally recognized, which eliminates confusion for interested parties when discussing a particular substance that may have several chemical structures, common names and molecular formulas. The database is updated daily, making it the most authoritative resource for CAS numbers. Approximately 15,000 unique substances are added to the database daily, with information from scientific publications and patents.
A typical entry in the CAS registry for a substance provides the CAS number, synonyms, molecular formulas, experimental data, diagrams, ring structures and all referenced literature. The database covers substances from scientific literature and patents dating back to the early 1900s. Additional databases provided by the Chemical Abstracts Services provide more specific information relevant to a particular field, including databases of chemical reactions, regulated chemicals and chemical suppliers.