CRC Handbook of Chemistry and Physics The authoritative reference source on chemical and physical data.
The Merck index : an encyclopedia of chemicals, drugs, and biologicals A one-volume encyclopedia of chemicals, drugs and biologicals.
Lange's handbook of chemistry Properties of approximately 4,400 organic and 1,400 inorganic compounds.
TOXNET: toxicology data network A database of hazardous substances, with comprehensive, peer-reviewed toxicology data for about 5,000 chemicals. Definitive reference for chemical and process engineers.
Knovel Critical Tables Interactive charts and tables that allow you to export property data.