For information on thermodynamic data for over 5,000 chemical compounds and on ion-energetics data for over 10,000 chemical compounds, NIST's Chemistry WebBook is available for searching. Compounds can be searched by name, chemical formula, or CAS (Chemical Abstracts Service) registry number. Information on enthalpy of formation, heat capacity, entropy, ionization potential, and appearance potential is available. Note that this site works best on browsers that support tables. NIST also supplies reference databases in the area of physics.