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| CATEGORIES ABOUT CAS REGISTRY NUMBER | |
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'' Chemical Abstracts Service '' (CAS), a division of the '' American Chemical Society '', assigns these identifiers to every chemical that has been described in the literature. The intention is to make database searches more convenient, as chemicals often have many names. Almost all molecule databases today allow searching by CAS number. As of May 2nd, 2006, there were 27,926,007 substances in the CAS registry — the current number is published here . Around 50,000 new numbers are added each week. CAS also maintains and sells a database of these chemicals, known as the CAS registry. FORMAT A CAS registry number is separated by hyphens into three parts, the first consisting of up to 6 digits, the second consisting of two digits, and the third consisting of a single digit serving as a Check Digit . The numbers are assigned in increasing order and do not have any inherent meaning. The checksum is calculated by taking the last digit times 1, the next digit times 2, the next digit times 3 etc., adding all these up and computing the sum Modulo 10. For example, the CAS number of Water is 7732-18-5: the checksum is calculated as (8×1 + 1×2 + 2×3 + 3×4 + 7×5 + 7×6) = 105; 105 mod 10 = 5. ISOMERS, ENZYMES, AND MIXTURES Different s has 9031-72-5. An example of a mixture with a CAS number is Mustard Oil (8007-40-7). SEARCHES When using CAS numbers for database searches, it is useful to include the numbers of closely related compounds. For instance, to search for information about Cocaine (CAS 50-36-2), one should include cocaine Hydrochloride (CAS 53-21-4), since that is the most common form of cocaine when used as a drug. SEE ALSO
EXTERNAL LINKS
To find the CAS number of a compound given its name, Formula or structure, the following free resources can be used:
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