Chemical Engineering

Free but requires registration. Search by common or trivial chemical name, chemical formula, molecular weight, or CAS registry number. Structural searches are possible using a Simplified Molecular Input Line Entry System (SMILES) in which 2- and 3-dimensional chemical structures are represented in linear textual format. Information includes chemical structure, melting, boiling and flash point, specific gravity, vapor density, water solubility, RTECS, DOT, and CAS number. (From PerkinElmer Corporation.)

Directory of chemical substances. Search by name, registry number, formula, classification, or locator code.

Search chemical structures and drawings. Note: does not accept common names.

From the National Institutes of Health. Find the chemical structures of small organic molecules and information on biological activities.

Information about chemical elements and compounds (structures, properties), compare elements and compounds, compute properties of chemicals and solutions.

Up-to-date interactive table, providing lots of additional information, including background information, compounds, electronic properties, physical properties, crystallography (with visualization options), nuclear properties. Download printable versions.

The Royal Society of Chemistry offers a stream-lined, interactive version of the periodic table.