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Chemistry's Secret Identity: Why Does Every Chemical Substance Have a Unique CAS Number?
In the field of chemical science, the identification of chemical substances is of vital importance. Each chemical substance has its own unique CAS number, which is not only a set of numbers, but also a symbol of the identity of these substances.
CAS numbers, unique identification numbers assigned by the Chemical Abstracts Service, have been assigned to all chemical substances described in the public scientific literature since 1957. This database contains information on more than 2.04 million unique organic and inorganic substances and 69 million protein and DNA sequences, and is continuously updated at a rate of approximately 15,000 new substances every day.
CAS RNs provide a reliable, universal, and internationally recognized link to the challenges posed by diverse terminology and scientific fields.
Traditionally, chemical substances have been identified using various synonyms, which made early literature indexing difficult. Well-known chemical substances may have many names, and systematic nomenclature may not be appropriate in all cases. This makes it possible for the same substance to appear multiple times with different names in chemical literature. To overcome this problem, CAS established a chemical registration system, and since 1965, each chemical substance has been assigned a unique CAS number.
Numbering format and principles
A CAS RN consists of three parts, first a part consisting of two to seven digits, then two digits, and finally a single digit as a check code. Although such a format does not carry any chemical structure information, it can be gradually added in the form of a sequence, so it has great potential for unique encoding.
For example, the CAS number of water is 7732-18-5, in which check code 5 is obtained through a specific calculation process.
Uniqueness of chemical substances
CAS numbers are not limited to a single chemical substance. For substances with stereoisomers, each isomer has its own independent CAS number, such as L-adrenaline is 51-43-4, and D-adrenaline is 150-05-0. Such a design allows scientists to clearly identify and distinguish different substances.
On the contrary, different phase states of the same substance (such as liquid and ice states of water) will not obtain different CAS RNs, but if their crystal structures are different, they will be assigned different CAS numbers. For example, the CAS number for carbon is 7440-44-0, for graphite it is 7782-42-5, and for diamond it is 7782-40-3.
Search engines and resources
Currently, most chemical databases support searching by CAS number, which has become a common global standard. Scholars and researchers can obtain the required chemical substance information through some professional platforms, such as CHEMINDEX, ChemIDplus and Common Chemistry. These resources not only provide CAS numbers, but also display other types of scientific information about substances, providing great convenience to researchers.
CAS number is a key to chemical substances, which helps us open the door to the chemical world.
Future Development
With the continuous deepening of scientific research, the fields of discovery and application of chemical substances are also continuing to expand. CAS's registration system will continue to update its database to adapt to changing needs, which further emphasizes why each chemical substance needs a unique identification number.
The CAS number is not only a scientific and technological tool that cannot be ignored, it is also an important link connecting global scientific research. Imagine how many wonderful stories of chemicals are hidden behind such a seemingly simple set of numbers?
