Thanks for all the feedback on CAS Number lookup. It was right to point out that there are millions of CAS numbers - so my search for a simple database seemed hopeless. But most of us, most of the time, are dealing with 'ordinary' chemicals so I'd thought that a database able to cover, say, those listed in the CHIP regulations books might be readily available. Wouldn't it be an act of kindness for someone to issue such a simple list? Of course one can pay to look up these numbers with STN etc. - but I was looking for something free for my own PC. Although I looked at quite a few web sites with free CAS Number lookup, none was much use. But the ECDIN site recommended by Michael Barker (thanks!) was superb. It gave a 100% hit on the odd selection of numbers I threw at it - plus it gives lots of other data. Today it says it is changing its URL from http://ulisse.ei.jrc.it/Ecdin/Ecdin.html Unfortunately the message telling of the change is ambiguous. It's either: http://ulisse.etoit.eudra.org/Ecdin/Ecdin.html or just http://ulisse.etoit.eudra.org as of a few minutes ago the first one worked and neither of the second two did, so I don't know when the swap will take place. Many thanks for all your help Steve Steven Abbott steven@abbott.demon.co.uk http://www.autotype.com chemweb: A list for Chemical Applications of the Internet. Archived as: http://www.lists.ic.ac.uk/hypermail/chemweb/ To unsubscribe, send to majordomo@ic.ac.uk the following message; unsubscribe chemweb List coordinator, Henry Rzepa (rzepa@ic.ac.uk)