The Chapman & Hall Chemical Database (CHCD), formerly HEILBRON, the chemical properties database, represents the complete text of several chemical dictionaries from Chapman and Hall. CHCD is a source database of chemical identification, physical-chemical properties, use, hazard, and key reference data to the world's more important chemical substances, as selected by a panel of experts. CHCD provides chemical substance identification through searching physical and/or chemical properties, compound variants, derivative names, synonyms, CAS?/sup> Registry numbers, molecular formulae and molecular weight, biological source statements, use/importance data, melting point, freezing point, boiling point, solubility, relative density, optical rotation, and dissociation constants, as well as providing suppliers and toxicity data.