Zusammen

Next up in our survey of free chemistry databases and services on the Web is Common Chemistry from Chemical Abstracts Service (CAS). Common Chemistry is a recently-introduced database that contains naming information for about 7,800 commonly-used compounds in industry and research.

You'd use Common Chemistry if you had in mind the name or CAS Registry Number of a particular widely-used compound. For example, searching for the name melamine gives a results page on which the second entry appears to be to one most of us would be thinking of. This page lists a number of other synonyms, as well as a 2D chemical structure at the bottom.

An interesting feature of Common Chemistry is its relationship to Wikipedia. From the Common Chemistry site:

CAS has collaborated with Wikipedia in developing this resource and encourages you to use the Wikipedia link (when available) or other sources of general information on chemistry, to learn more about these chemicals.

Unfortunately, I was able to find few Wikipedia links in the current version of Common Chemistry. For example, the melamine entry described above does not link to the Wikipedia page for melamine, but the entry to formaldehyde does have the relevant Wikipedia link.

CAS has selected entries for inclusion in Common Chemistry based on citation frequency. In addition, all elements are included:

This database contains the CAS Registry Number®, chemical names (both formal and common), molecular formulas, and structures or sequences for ~7800 chemicals of widespread general public interest. These substances are of global commercial use or importance and have been cited 1,000 or more times in the CAS databases. Examples of substances included are aspirin, biotin, benzoyl peroxide, and boric acid. The Common Chemistry database also includes all 118 elements of the Periodic Table, although not all of the elements may meet the 1,000 references threshold.

Common Chemistry contains less than 0.1% of the entries in the CAS Registry. Nevertheless, it is the only free, authoritative source on the Web for information on CAS Registry Numbers.

Kudos

• Freely available information on certain CAS Registry Numbers.
• Easy to navigate and responsive site.
• Focused design with minimal CAS marketing distraction.

Ideas for Improvement

• Place the chemical structure at the top (rather than the bottom) of record details.
• More consistent linking to Wikipedia.
• Link out to free databases in addition to Wikipedia.

Credit: thanks to Antony Williams for bringing Common Chemistry to my attention